About your alien invasion example, I think you might be a bit exaggerating the difference between 5e and 4e. Antimagic fields and other fictional elements that cause penalties or prevent actions could exists in either. I have to note that the element that caused disadvantage to basically all rolls seemed to be designed to punish non-caster (or it does, whether the GM intended that or not) as many spell effects just work without a roll and thus are unaffected. Not sure how relevant that is for agency, except that it might have caused some frustration in the players as their sensible-seeming attempts kept failing due this effect.
My main observation was how you described 5e method of assigning DCs and such as 'arbitrary' compared to clear level appropriate guidelines of 4e. It is funny, because I would describe them as completely opposite manner. In 5e the DC actually represent something concrete, they're reflection of the fictional reality, whereas in 4e they're just arbitrary and do not represent anything concrete beyond being sufficiently challenging to the players (I think they tried to walk back that in some of the later material.)
Now, considering that you were running a scenario written by someone else, containing a lot of atypical elements, I can understand how it might feel 'arbitrary' in that context. What is the proper DC (or even skill) for operating alien hoverboard in D&D? Who the hell knows, there normally even aren't alien hoverboard in D&D! But with a GM who has a good mental picture of the setting, consistent(ish) approach for assigning DCs and players who are familiar with this it is not arbitrary. The same task will have the same DC regardless of the level of the character attempting it.
Alright, lots of stuff.
Going to start with some misconceptions that you have of 4e (I'm presuming you haven't read it or run it?):
1) There is no such thing as the classic Antimagic Field in 4e. Its not in the DMG, DMG2, or any of the Dungeon Magazine articles. Its not a Ritual in any of the PHBs. Its not in any of the sourcebooks. Also (and these are lost to us now) I'm very confident that this was specifically called out in the design articles and was a HUGE point of contention for certain GMs (that like using Antimagic Fields and such) 13 years ago or so. I'm fairly certain it was called out as "not fun" (in the same way that Sneak Attack/Backstab/Criticals not working on Constructs and Undead and Elementals is "not fun"...a separate article) so the game was designed with intent to not have them. The game is balanced such that all characters recharge their abilities the same and all characters are on the same power curve. There was (again) a huge point of contention for some fans. Some thoughts:
a) Even if you wanted to erect some kind of classic Antimagic Field, the game would seriously fight you (not just in your own hacking, but also in the corner cases that would come up in said hacking - do Constructs, Elementals, Undead come apart...which Monster Powers are affected, and in actualizing it in play...the impacts of a Wizard having only the MBA of a dagger and the RBA of a Crossbow on the Combat Encounter maths and on the duration-dragging of combat would be SEVERE) because of the Keyword tech and the way the game is structured.
b) There are EXTREMELY limited 4e iterations of the classic Antimagic Field and they are cordoned off to the Traps/Hazards section. These are very specific and codified things (like all of 4e). The Entropic Collapse Hazard for instance. Any creature carrying a magic item or using an Arcana Keyword Power (a "Spell" in 4e) has an Attack vs Will. Its a very (relative to classic Antimagic Fields) small Area of Effect and it doesn't shut down magic like in days of yore. It does level-equivalent damage and dazes (save ends). And, because it is a Hazard, it has an Experience Point value (based on its details, which includes the size of its Close Burst 5 Attack) that gets folded into the Combat Encounter Budget (which is a very codified thing).
So yeah...I can feel you thinking/saying aloud "TTRPGs are art, not engineering and this is why I hate/didn't play 4e."
There are no classic Antimagic Fields in 4e. And that is a product of intentful design, not a happy accident or omission.
2) You have the same confusion over 4e DCs as many others who didn't play it or were smuggling in the system engineering/architecture from other systems (D&D of yore perhaps). We had many, many conversations on these boards regarding subjective vs objective DCs, with many who hated or didn't understand 4e framing things this way. Here is the reality of 4e's DC system:
a) It works exactly as many indie games do. Port the philosophy of PBtA or FitD games directly over to 4e where, from first principles, the core mechanic is there to challenge THESE PCs and scale with them. Everything is about the framing. For instance:
In Dungeon World the core mechanic is always 2d6+ x vs 6- (failure and mark xp), 7-9 (success with cost/complication), 10+ (success). These numbers don't change, but the PCs do. What changes are "the conflicts, and their attendant obstacles, that you will be framing the PCs into." THIS will scale with the PCs in the exact same way that monsters scale in the story of D&D that the PCs go through (you fight goblins > orcs > trolls > giants > dragons). For noncombat obstacles it might be parleying with bandits/pirates > town elders > the king or his archmage > an angel/devil or dealing with a trapped oak door with town guards > an aware door that animates the entire room > dispelling an open portal to the Far Realm, with horrific aberrations undulating into this world, that a mad Sorcerer has conjured to end the world.
Exact same thing happens with 4e. The DCs scale with the PCs. Oak doors w/ town guards still exist (as does the Heroic Tier DCs that you used for the scene many moons ago)...but you aren't going to be dealing with that conflict at Epic Tier when you're dealing with mad Sorcerers, Far Realm horrors, and open gates to the insanity therein. If, for whatever odd reason (and by "odd reason" I mean "GMing error"), your Epic Tier PCs are dealing with the mundane conflict of a town...you just "say yes" to action declarations. You don't need to "roll the dice" (consult the resolution mechanics). Fighter pulls the door off the hinges and threatens the guards? The door is off the hinges and the guards are cowed. Done.
4e DCs and PC Skill #s are all about genre framing, genre logic, and testing the PC archetypes within that genre milieu.
On 5e and the game above:
1) As you noted, not my game so I couldn't tell you the reason why the GM constructed things the way they did. My guess is, however, that (a) he was mapping the effects that he has in his head for the scenario onto 5e's mechanical architecture and (b) he wanted to make things very difficult for the players.
One thing you missed in the play excerpt is that the Wizard suffered significantly as everything had Magic Resistance (so Advantage against his spells). So pretty much every dice roll and action declaration for all the PCs suffered. By no means did running this session feel like it was unfair in particular to any of the particular classes there (Fighter, Rogue, Wizard). They all felt pretty equally boned.
2) I mentioned the 5e DC 30 (?) thread that I put together a long time ago. Many, many 5e GMs were involved in this. There was no consensus on anything. Answers in terms of DC setting about everything under the sun in were all over the map (which I expected going in...it was more or less a Rorschach Test for the system and the people running it). In fact, if anything, that thread showed just how profoundly disparate across tables the handling of even seemingly mundane or innocuous things were (jumping high, jumping long, enduring x, etc); both input/procedures for DC setting and the actual output (the DCs themselves) of those procedures. The reason for this (and what I was trying to get at in that thread) is that 5e's GMing ethos is informed by some combination of (a) Rulings Not Rules (its up to the individual GMs) while (b) simultaneously trying to thread the (ever evasive) needle of Genre Logic Married to Naturalistic Simulation.
The arithmetic of (a) + (b) creates WIDLY different handling from various GMs on an action declaration to action declaration and obstacle to obstacle basis. That (b) is particularly fraught (which was what I was trying to disentangle in that thread). That is your "art." And because it is "art", its extraordinarily difficult to not lead to contention and a sense of arbitrariness...PARTICULARLY as play moves up toward the Epic Tier of 5e. I mean this is where the Far Realm conflicts or Modron/Planescape conflicts come into play. Due to genre, there will invariably be biology infused alien tech here ("tech" meaning infrastructure, gadgets, means that the civilization deploys). Forgetting those kinds of things for a moment, even dealing with the deranged machinations of Demons or the detached cosmical power of Primordials or Elder Spirits (and all of the crazy environments they inhabit) is completely non-intuitive.
Somehow, that (ever evasive) needle-threading of Genre Logic Married to Naturalistic Simulation must occur...and it must be actualized in a way that is coherent and functional sufficient to facilitate the actual playing of a TTRPG (meaning players need to be able to infer or intuit DCs within a pretty narrow window and then make informed action declarations for their PCs accordingly...or the whole agency thing goes tits-up).
On your last statement:
As for the second quote, I am not quite sure what your point was there. If it was to point out that in 5e there are many different way in which the GM could apply force if they so chose, then that is not in dispute.
That is precisely the conclusion that I was building toward! So we're on the same page!
So, to be clear, you do in fact believe that the below aspects of system/GMing are indeed vectors for Force and as you move toward the left, you're introducing more and greater prospects for Force (or outright ensuring the manifestation of Force during play):
latitude vs constraint
mandate vs verboten
opaque vs transparent
unsystemitized (Rulings not Rules) vs codified
GM-facing vs player-facing