AFAIK, and I don't want to go trying to find Meta threads to support all this, but these summarise my feelings after reading quite a few over the past year or two:

StackExchange (SE) announced that users must start being polite and welcoming to beginners and new users, trying to address the perception of hostility and unfriendliness. Generally coming from a well intentioned place, but without good plans for how that would work, except declaring "be nice" and hoping that would do it. There is a break of opinions between "a new user should have a welcoming experience" (both sides - company and users - agree) and "there is an endless flood of 'give me the codez' and homework questions and spam, we're wading through the garbage to your company benefit, and now we get criticism that we aren't doing your dirty work with a smile on top, please acknowledge" (many users agree, the company refuses to engage), and "blunt technical answers are not impolite" (company refuses to engage). SE's unresponsive stonewalling or ignoring questions and suggestions annoys users.

When mods complained about the lack of support from SE, e.g. long standing requests for moderator tools with better UIs, or more guidance from SE employees, SE ignored them.

SE announced that they were retroactively relicensing all content. When people objected, questioned the legality, asked for clarification of specifics, SE ignored and did not answer. It appears they have done this once before, and did not engage then either, but this time might be more serious.

When there was an increasing number of people sharing their bad experiences with SE around the internet, SE more or less blamed the users, and when the users suggested ideas to improve SE in various ways around this (e.g. changes to the flow of onboarding new users, which SE was trialing on some sites), SE ignored and didn't engage.

SE rolled out a new Code of Conduct and insisted everyone will respect people's pronouns[1]. Long standing, well respected, polite, moderator Monica Cellio stopped being a moderator in uncertain conditions, but AFAIK she tried to use gender-neutral language when someone's gender was known, and SE steamrollered her for it.

As a result of her loss of moderator status, several other moderators have either stepped down in protest, or signed an open letter revealing many complaints about how SE has been interacting with moderators - or not interacting - in the private mod/company chatroom which normal users can't see.

Many times through these arguments, an SE employee or two has put out some corporate fluff feelgood non-answer which ignores all raised issues and restates some platitudes or fiat-idealism, which users have taken as worse than silence and/or an insult.

There is a general feeling/suspicion/conspiracy theory that SE is setting itself up to be sold for huge piles of cash, and is trying to stamp out rudeness, appear welcoming, "clear up" licensing concerns, shrug off squeaky-wheel users, and absolutely not say anything controversial, and that SE either has no coherent leadership and direction for the future, or has one they know the users will object to and are therefore silent about it.

Involved in this, although I don't have any idea how closely involved, is SE's spread from purely technical topics to a much wider range of sites covering politics, religion, hobbies and more general interests.

[1] https://stackoverflow.com/conduct says "Be inclusive and respectful. [..] Prefer gender-neutral language when uncertain." and "No bigotry. [..] Use stated pronouns (when known)."

----

Edit: One of many rant/complaint posts full of links you can dive into: https://meta.stackexchange.com/questions/333965/firing-mods-... which leads to things I missed - the forming and firing of a team to engage with developers in 2017, the redesign of sites making them "worse" while ignoring the user feedback, a single Tweet leading to taking a site off the hot questions list an dropping 80% of its traffic without announcing anything to the site users ("Stack Exchange cared more about how they're perceived by a single person on Twitter than what effect making a change like that would have on a site, and didn't care enough about the community to even let the general IPS community know about the change"), and the statement from employees "Stack Overflow Employees have panic attacks and nightmares when they know they will need to post something to Meta" where the company defended themselves by moving somewhere they don't have to hear the (overly personal) criticism at all.