Yes, but what sort of martial? "Martial" is a very broad bucket term, it's not a character concept. How are you going to discuss the mechanics of what a char can do, vs what it should be able to do, if you don't have a concept to relate it to ?
Should a martial be able to fly ? Should a martial be able to create earthquakes ? Should a martial be able to power word kill ?
How would I know how to make an assessment of those things ?
Should a barbarian of the storm be able to throw around lightning bolts ? Ooh, now that I can see, b/c it totally fits the concept. Let's have a mechanics discussion about how much dmg those lightning bolts should do and also a story discussion about how it happens - do primal spirits fight for/with them, do they channel the power of their ancestors, does their rage manifest in physical elemental form, etc. Should a barbarian of the storm be able to change into a dragon ? Umm ... no I don't think so, because I can't see any link to the char concept.
Should a draconic instinct barbarian be able to transform into a dragon ? Oooh, yeah that might work, let's a conversation about the mechanics of the dragon form to ensure it's balanced and a story conversation about how it happens - does their rage make them forget their identity and an ancestral one takes over, etc. Should a draconic instinct barbarian be able to throw around lightning bolts ? Umm ... well .... probably not because it doesn't seem to fit the concept.
See what I mean ? To me, in order to have any sort of meaningful dialog about mechanics, I would think we need to understand what sorts of char concepts those mechanics relate to. Not every martial character should be able to do every sort of supernatural, fantastical, magical thing that exists just b/c they're "a martial". So what should they be able to do ? Well, it depends on the char concept.
Generally, Fighters are the "typical example" of a martial character, although by no means the only one. It is very much worth noting that not all fighters are pure martials: Eldritch knights, Rune Knights, Echo knights are all examples of fighters that aren't purely martial any more. Rogues and Barbarians have similar specific subclasses in the same manner. Classes like Paladins, Monks, Rangers are also all explicitly magic users and so are generally viewed more generously when it comes to allowing them to pull off unusual ideas through use of their class abilities.
Of course. But this has nothing to do with whether the character is a martial or a caster. This is about getting DM buy-in to play a char concept that has implications for the shared world. You would need this regardless of whether you are wanting to play a martial or a caster.
No. This is about whether martials get to have non-combat power within the game at the same level that spells grant the spellcasters, without needing to get DM buy-in.
You gave the Tony Stark example as an example that a martial
doesn't need DM buy-in to be as effective in non-combat situations as a spellcaster; "Take away the suit (magic item) and what is left that is just granted by class features?
I'm guessing that you didn't intend to move the goalposts, and you just forgot where that example came from. But it does kinda prove our point.
Ok, now
this is something we can have a mechanics discussion about !

What would be the big caster items ?
Staff of Power & Robe of the Archmagi ? +4 AC, spell attack and save DC - the spell save DC is likely to go from 18-ish up to about 22-ish
What about for martials ?
Pick any 2 of the following: Armour+3, Shield+3, Weapon+3 & Belt of Giant Str (I guess depending on whether you're going for offense of defense or a mix of both ?) - those are pretty impactful too.
Do you think they make way more difference than the caster ones ? I'm not convinced that's so.
They make no appreciable difference than the caster ones.
Because both are almost entirely combat-focused.
So in a discussion about how martials generally need the DM to grant them magic items to perform as well out of combat as the spellcasters without items do, you chose to
only allow combat-based items to be considered for the comparison.
There are any number of magic items that would have been germane to the subject at hand that would have made a massive difference in out-of combat performance for the martial: Apparatus of Kwalish, Carpet of Flying, Cloak of Invisibility, Cubic Gate, Helm of Teleportation to name a few.
But you chose to only allow items for the martial that give basic numerical bonuses, primarily only useful in combat, to be used for the comparison.
Why?
LOL no, that was in reference to whether the game rules support being able to play the character concept you want!
Really? It would seem that they do not in this case.
Agreed. Although, again, if the player wants to play Batman in D&D, and the DM is on board, why not?
Generally because playing a batman-equivalent would require not only way more gold than a character can start with, but also either magic items or spells to replicate the many gadgets that he relies on. Since magic items aren't generally easily available for sale, and having spells takes the character out of the purely martial realm, this rather proves the point that a martial would need DM generosity to play a concept that many casters could
without needing the DM to put their thumb on the scales.
Ok, then I haven't managed to get across what I was trying to. I was trying to say that the char concept should come first, and then the mechanics should be evaluated against that, not just in a white room vacuum.
eg, if a player wants to play a Stalwart Guardian type character, there's not a lot of point of comparing the DPR output of this character compared to a blaster sorcadin and saying "See ? The martial gets the raw end of the deal again!"
Does that make more sense ?
That statement does indeed make sense, but it has very little to do with what was being discussed.
Gammadoodler brings up the example of Morgana as a fully developed character with effective ways of influencing and taking part in non-combat challenges. As compared to King Arthur, whose influence and capability to deal with high-end non-combat challenges has to be granted by the DM because it is not given by class features.
Another fighter has very little effectiveness in such challenges unless the DM
also gives them that ability, whereas another spellcaster still has that capability baked in to their class.
Without availability of useful magic items in the form of scrolls to write into their spellbooks, the wizard is a glorified sorcerer, knowing only 2 spells per level, not something that allow the broad appeal of the wizard, able to perform in any situation if given enough advance notice.
Wizards get to learn 44 different spells at base. That is almost three times more than a sorceror. They are fine without finding any scrolls - extra ones are just a power boost rather than being necessary. Heck, a wizard even gets to memorise a lot more spells than a sorceror, and cast more in a day.