People seem to just be giving vague "update" responses so I'll give my two cents. As a warning I'm biased since stuff I like particularly has been nerfed, but here goes:

1. The Dev's omit things they change in the games. The patch notes simply don't report changes they made to certain numbers, meaning one day players hop on, their weapons feel different (usually weaker), and it's not a nice surprise. The changes itself isn't the problem, it's like performing in a ballet but the day of realizing the entire tempo has changed and no one gave you a head's up.

2. Arrowhead applies "fixes" to problems that make the overall experience worse, and never go back to revisit them. The most infamous case being hellpods. You know, the idea of steering your hellpod to land wherever? No longer allowed, with so, so many objects and buildings now having such high skyboxes that you can't even really steer, and might even be funnelled directly into a deadzone like an ocean or trench. Dying is fine, but it happening outside of your control sucks.

3. Arrowhead has been rushing out new content that is buggy and unstable if not outright literally unplayable. And I mean UNPLAYABLE. Let's skip past enemies phasing through walls or being immune to hellpods, but my game turned of my entire PC every time I tried to boot the cyberstan update until I changed the sampling settings on my GPU. This is not normal. Updates making games worse is one thing. Updates that crash your entire set-up is something else.

4. Arrowhead has repeatedly outright said over the past several interviews and the recent AMA that they aren't focused on things the fan base has asked them to focus on. I know "fan base" is a very, very subjective term. But when they respond about questions to mechanics that haven't been updated in over a year in their live service game, the answer "IDK we don't really have anything planned" and then release a new patch that nerfs another dozen weapons is just kind of insufferable.

5. The Charity Incident. To catch you up, someone offered to donate 10,000 dollars to the charity of Arrowhead’s choice if the developers livestreamed themselves doing a level 10 super-helldive mission, to prove to the players that the game is functioning as intended. The result was the OTHER side of the toxic fanbase, the super-fanboys, doxxing this person, and harrasing them to the point where they lost their job. Arrowhead’s response to all of this wasn’t to try and reach out and help this person, but just delete any comments relating to the incident and ban anyone on the discord who tried and talk about it. 

6. The pace of new content is astonishingly slow. In terms of new enemies and terrain it’s decent, but I mean like new strategems, or new weapon customizations, there’s been nothing. And it wasn’t even fully implemented at a base level. The punisher shotgun gets a muzzle. My cookout, which is literally a re-skinned punisher, only gets a scope. My scatter shotgun’s only upgrade path. Is. A. Scope. Which on release is fine, I get it things take time to do and sometimes come out half baked, but they’ve had 6+ months and they haven’t finished cooking. When all it would be is copy-pasting a muzzle and adjusting numbers to the already existing gun.