I find it a bit amusing that D&D appear to have the quality that in all it's iterations the most fun way to play it was not the one it was designed for.
TSR era D&D was designed for a dungeon crawl suspence curve with encounters as quick events along the way, the boss fight at the bottom as the twist, and the heroic escape through wandering monster filled tunnels with the loot but no resources as the frantic climax.
However most players seemed to think it more fun to play it as a mainly freeform fantasy storytelling game.
I am not sure it was designed as a dungeon crawler. It was a wargame at the level of individual units and the first adventures were dungeon crawlers, but that changed with Tracy Hickman at the latest, still during the 1e days.
It supported dungeon crawling, but I am not sure that was the design focus. I am not even sure I would call 1e designed. To me 3e was the first actually designed version, the ones before were organically evolved / mutated / hacked together more than designed.
Then 3ed came along with its game designed to sell booster packs for a
deck character construction game where the main focus was to get an interesting interplay between players' out of session planning and the climax of seeing how those plans played out at the table.
However most players seemed to prefer playing it as a somewhat structured storytelling game.
so it was played essentially like later 1e and most of 2e was
The char construction part to me was not so much design choice as a consequence of wanting to sell supplements, and arguably 2e did this more with all the Complete Handbook of X stuff
Then 4ed came along, designed as an encounter focused game, complete with mechanics for heating things up once the participants hit bloodied.
However these strong mechanics for having long cool battles sucked time from what most players wanted - storytelling. So many stayed behind rather playing the deckbuilder that were less in the way of their storytelling. And those that went to 4ed appear to mostly think the best way to play it is mostly freeform storytelling with a big climatic combat every few session.
I think 4e is the first one where game design and what players wanted actually clashed, at least for a large enough percentage, others loved it for those changes
Then we have 5ed where my impression is that the idea was mainly "OK, just let us make a stew of everything people say they like from the past, design be damned". Hence we sit with a game that isnt really designed for anything, but incidentaly appear to be the most suitable version of D&D for what most people want to play.
by basically returning to what 1/2/3e did, so it again gets played more or less like any version before it
I am hence unsure if the lack of escalation can be considered a flaw. Yes, cinematic climatic combat encounters certainly is better with it. But any such mechanics adds complexity to the game that is not needed for one round blast away the enemy showing how cool we are before continuing the story encounters. And my gut feeling is that it is this sort of encounters that is the bread and butter for the way most like to play...
I am not sure it is needed either, I understand wanting a climactic end fight, but that to me is more about encounter design and barely making it than trying to funnel chars to do things in a certain way to build to a climactic last round where they can use their superpowers.
It is climactic for barely making it, not for reversing the sequence in which events during the fight happen