Is there a link for that Balor thread? What exactly did the DM give the party to make a CR 19 beatable? Such as handing out vorpal weapons and defenders and +3 plate?
I'll assume that's a question.
I would counter by going one step further - There is more to the game than character advancement. I would go so far as to suggest that blatant character progression can detract from the role-playing experience.
But on the other hand, an obvious path of advancement is an easy way to hook players and keep them coming back for more. I don't want to call that the WoW mindset, because it became apparent as soon as 3.0 came out and offered every class with new abilities at each level, but similar principles are involved. Indeed, one of the criticisms of certain games - Shadowrun, Rifts, etc - is that your characters never really progress past what they are at the start of the game. To that end, character advancement can be a useful method for getting players invested in their characters.
And you lose that when you no longer progress from a +1 sword to a +2 sword and then a +3 sword.
It has more to do with the fact that the Balor is pretty weak for a CR 19, since so much of its power calculation comes from its Death Burst.
I think that depends on the campaign style more than the game edition. My players can anticipate finding particular wondrous items, because by and large the way they find items is by going on quests specifically to track down those items. (Coincidentally, they're deep into a quest for an invisibility item right now, although it's a mask rather than a ring.) Quests for better weapons and armor work the same way.And on that note, wondrous items are difficult to anticipate. Maybe you have a character who would really love that ring of invisibility, but that's just one item among the hundreds of magical items that exist in the world. You can't expect to find it. Whereas, in any previous edition, you really could expect to get the next +1 on your weapon. You practically knew that the day would come eventually, even if you never knew when it would happen.
Interesting- how has that worked, in general, with your groups? It has been my experience that having story-based magic items for a single purpose in an adventure (say, "The Sword of Cranberry" that will work to defeat the great Thanksgiving Turkey...), but people hate it when you regularly give then take their items from them.
I relate that only because I am reminded of a DM I used to know back in the day who would run Monty Hall (or Haul) campaigns and shower the players with stuff (Why not have a Hand with the Eye of Vecna?), then realize they were way over-powered, and devise a way to destroy it all... it all burned up in a fireball, or was stolen by thieves, or ... fill in the blank. After a while, the players got really tired of that, because it removed the fun.
So while I like the idea conceptually on occasion, I'm not sure it's a good long-term fix.
I think the bigger problem is that people view the only progression that matters is flat plus combat progression. That if an item doesn't have a "plus" it's not worth having. That's the sad part.
I think it should be made clear that 5e just doesn't work like that. Even your main proficiency bonus increases only four times in the course of 20 levels. It's not a game for people who want to see constant number inflation.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.