There tends to be huge amounts of overlap in what gamers enjoy. (...) Most people tend to fall under a similar umbrella.
This is verifiably not true, not within a single genre, not even within a single franchise. By the time gamers see changes that, say, Destiny brings with expansion N, expansion N+1 is already in production and N+2 is at the final stages of planning. So things may be "obviously" bad for people playing expansion N daily. But 1) things in production already depend on these "bad" decisions, 2) these decisions potentially lead to something important that end user simply doesn't see/understand yet, 3) large enough games (especially service ones) have more than one target group with conflicting "correct" decisions for them. Plus: 4) even if you correctly identify problem, chances are your solution wouldn't work but you don't have enough context to know that.
1) Let's say you're right that certain things are obvious. Unless you can address how production that takes gamers' feedback is supposed to be structured (in terms of work organization but also financing) things being obvious doesn't mean anything in real life.
2) You don't know what you don't know. Sometimes you need to jinx something small to build something greater on top of it. Gamers have little to no insight into the process behind the scenes so obvious conclusions are very often wrong with the benefit of hindsight and more data. Problem is: even if you get all of the background two or five years down the line, how likely are you to recall your bad, "obvious" takes and course-correct? Chances are by that time you've moved on and solidified your previous opinions about the title as facts. We all do that.
Alternatively you could have an extremely public development process where you essentially collaborate with the community on the game. There are very few successful examples of that (BG3, Warframe) and many more that ended up a joke/scam/vapourware (Em-8er, Star Citizen). And even if you're successful this is either built on pre-existing community and cash reserves (BG3) or, essentially, luck (Warframe).
3) This killed many games. The moment your GaaS is successful, you have at least two different groups of customers: hardcore metagamers and newbs. Their needs are drastically different and you can't have either without the other group. This is bound to generate different obvious solutions to the same set of problems.
4) This last point is a massive problem with gaming discourse these days. "Everyone's a designer" was a fun joke 20 years ago ("I've got a brilliant idea: GTA but in space!" - every armchair designer in early aughts) but it's an absolutely toxic undercurrent in gaming circles today. Fans of a franchise will write confidently about
obvious fixes a game needs for success or broader appeal. I mean, I get it, it's fun to think you know better than a bunch of devs who's done this stuff before, makes you feel special (and I don't mean - here or elsewhere - you specifically, it's a collective you). "Hire fans" and all that BS. Given how you can make a living talking online confidently about the things you don't know it is a real poison.
Single player games are not exempt from these problems. Building single player AAA experience takes money and time. And time is crucial here: you're designing game two to five years before it hits the shelves so you're essentially guessing what trends will be in the future. This often leads to bad outcomes through two separate paths. One: your financing structure forces you to make concessions about the design based on, say, publisher's likes and
current trends. If trends change, you're effed. Two: you're guesstimating what will be hot in 3 years or so based on your experience. This may work out, or not. That's why investing in franchises is so important these days: you basically shape perception of what your IP is or is not and can take safe risks with the changes you're making.