Broadly speaking, I do think these forums complain too much. With a few major exceptions (Royal Court, Legends of the Dead), CK3's DLC has mostly been good, with some exceptional standouts (Tours & Tournaments, Roads to Power). The team has shown us that they learn from their mistakes, too. Wandering Lords was easily the best Event Pack, and the Iranian Struggle feels much more interactive and less tedious than the Iberian Struggle.
The game still has serious problems, of course. It is much easier to exploit than CK2 was, even if the player is not trying. And there's definitely truth to the criticism that each major expansion adds unnecessary new mechanics and resources rather than expanding on what already exists.
I have great faith in the developers and their vision for the game. The consensus is correct; CK3 isn't CK2, and it doesn't need to be. It is its own game and I love it as much as I do its predecessor.
My biggest hope is that the devs will pay more attention to the overall cohesiveness of the game as time passes. I don't blame them for their focus on new content, and it's not as if they've entirely forgotten about prior DLCs. But the current "cluttered" feel of the game damages their vision and holds the game back from its full potential.
On an optimistic note, I want to remind everyone that many of CK2's best DLCs (Jade Dragon, Holy Fury) came very late in its development cycle; they helped tie disparate elements of the game together while revisiting topics like the Crusades. Mid-development major DLCs like Rajas of India and Horse Lords were absolutely panned at the time of their release... anyone who was on the forums at that time probably remembers.
The whole late game doesn't work because the AI is laughably bad. The conqueror band-aid is an insult, rather than a genuine attempt at improving things.
I don't mind CK3 not being MEIOU (/EU5), but I do think they've veered terribly off-course with the undue focus on 3d assets and totally random events as their substitute and vehicle for storytelling. There are better ways.
Really vehemently disagree with your last point. What's the point of a decade-long, nigh live-service development undertaking, if no lessons are learned and you can't, having just hit your stride, transfer your momentum but immediately stall out? When CK3 released, I had as little interest in at as Imperator at launch and went back to CK2 for probably two years because it was just totally empty. It's been a further couple of years, and outside the ERE, not that much has changed.
Point is, CK3 is progressing at an unbearably slow pace (I blame 3d assets) while extracting a really high price. No non-PDX GSG is nearly as expansive, and they offer similar levels of replay value. Not to mention that, for all their slow place, every update releases in an utterly unplayable state (a disgusting and reprehensible practice) and needs a month or two (!!!) to iron out really, really, really egregious bugs. That's just not up to par.
It's the year of our Lord 2025, and EU5, the emerging nation-state game, in which Europe outside of the HRE almost exclusively has Primogeniture, has implemented a better and truer to history inheritance system than CK3. The Tripartite Struggle is still resolved by confederate partition. Are you kidding me?
So many, so terrible abstractions. How the de-jure system interacts with inheritance makes no sense whatsoever and skews incentives in the weirdest and worst ways. But it's too much to elaborate on. It's easier to find a good system than one you wouldn't change in some, major way. Economy, warfare, inheritance, politics, religion, culture...