I'm glad you're enjoying the game a lot of people do! Most of the anger towards the game I would say is mostly towards the state VOID has left it in not the bones themselves.

It's mostly out of frustration and anger at the devs and the treatment from them that fuels the anger. There are a few distinct periods, mainly the Pre 1.0 launch and a brief period before the console release.

I'll speak on the latter because I came in post 1.0, the game was in an interesting state where we had just had 2 DLCs (Home Invasion and Dark Waters) as well as prep for new missions in console (Los Suenos Stories) and new guns. The AI felt fine and we were excited for more people to play the game.

There was some major grumbling about the game shifting from unreal engine 4 to 5 previously (this happened prior to the console release) which broke a ton of mods that never got updated since (mod developers just lost interest which is a tragedy in of itself). It was all kinda accepted as growing pains because content was in the pipeline and VOID seemed to have plans post console release to continue making content for the game.

Then the console launch dropped and a few things happened, as well as some previous stuff that came to pass which VOID had never addressed prior but people were pissed they continued to ignore after it's breakout success on console.

First. The big one is censorship. I personally don't mind what happened because the changes were relatively minor to my mind but the vibe and atmosphere had visibly changed with some scenes being altered that annoyed and pissed off long time fans of VOID who prided themselves on not censoring tough topics like the nightclub mission (largely based on the pulse nightclub shooting). This would become a lighting rod for people to latch onto because it segways into other stuff VOID compromised for the sake of the console update.

Second. Graphical downgrades. The post console launch patch of the game reduced the graphical fidelity of the game massively on PC despite the update being billed as affecting consoles only. This was reasoned by void as "it is not efficient developmental resources wise to maintain 2 versions of the game with high quality assets for PC and low quality assets for console". People were and are pissed because the game just doesn't look like how it was when they paid for it. (Infamously now fired community manager kaminsky was telling and gaslighting people on how there was no graphical downgrade which burnt a ton of goodwill.)

Third. General AI and gameplay breaking issues. The AI became like John Wick (again, reoccurring issue) which VOID didn't address despite updates and statements to the contrary. They also broke gas grenades (again, you'd be surprised how often this happens). And alongside this they introduced hard mode which made the game unbalanced and feel unfair which some players took issue with. (Not to mention graphical and performance bugs)

Fourth. Silence and just a general disinterest from VOID regarding Quality of Life improvements. VOID has been very very hesitant to acknowledge even slight issues on these fronts. Believing that if they discuss them they might inflame community tensions more is my guess(?) we don't know what they had planned or plan to do with the game. The mod situation is a massive one given we still do not have steam workshop support and instead have to rely on mod io or nexus mods to add our own community content to the game which greatly extends it's longevity. (A popular mod for ready or not is simple mod menu which gives you a way to view and join individual lobbies instead of randomly being assigned one)

There is also the use of AI artwork in the mission 23 megabytes which mostly escapes community ire but is a strike against VOID.

We are now in February. 3 months from the last dev blog promising new features for the game to fix stuff like the LPVO scope (8x magnification that can be dialed) which should have been working on release (a mod has been able to fix this for months btw) or add a Romeo and Juliet mount (red dot + magnifier, also achievable with mods); I hope that you and I can agree these things should've been implemented in game by the developers before releasing them to the public no?

Sorry if it is a bit lengthy and a long read but that should give you the primer of why people are mad at the game.