Not really off the top of my head so I'll elaborate on the points I've already made to demonstrate why I think these things are such an issue. It also goes to show that with a few minor changes, Mojang would be able to balance these things super easily.

Portal based farms are really the worst culprit, imo. It's the meta for loads and loads of different mob farms and just consists of a cube of portals making all these once separate farming concepts basically the same. They're also incredibly overpowered and yield huge amounts of items. I remember back in the day people spent lots of time perfecting the designs of their big farms and there really hasn't been much interesting development in the tech community because portal based farms are super fast, easy to throw together, and get you more items than most other designs. I think removing them would force people to be more creative again. This is a pretty common sentiment in a large part of the tech community. Here are a couple of portal farms and you'll see that things get boring real fast:

Slime: https://youtu.be/cerBKl6Gzeg?si=27PPAqpeVaOmJ8ID

Guardian: https://youtu.be/n_IH6LUYyMk?si=fAtOK47fv-5Qhjvs

Ghast (I'm on mobile so I can't timestamp but you can skip about 30mins in): https://youtu.be/ZlefdidnABI?si=H7Rlhb3yKIB8SyVp

Wither skeletons: https://youtu.be/Dj5JedJuXrY?si=7JjKvU5uMYlmY3Pz

There are quite a few more mobs that can be farms in the same way but I think that proves the point enough.

Raid farms tech has also gotten absurd lately if you check out this: https://youtu.be/owuP8P4s_8g?si=2sjTYPAHNG0dVcfi. That farm produces hundreds of thousands of items per hour and can be built in an hour or two. The raid stacking mechanics are really overpowered. I think raid farms should definitely be a thing and some of the simpler designs are decently balanced but stacking farms are game breaking. For reference, this farm yields more witch drops than scicraft's witch farm project which took years to finish.

I'm really just speaking in terms of my little niche corner of the game. Nerfing portal based farms or stacking raid farms wouldn't really effect anyone outside of technical players because it requires some obsidian farming setup as a barrier or entry. Stacking raid farms, while easy to build for technical servers, are still a little bit above the skill level where it would be something casual players would build.

I know that you can always just not build these farms if they're boring, but it's really stagnated cool farm development in the entire community. It's more than just an individual decision because most tech servers these days just reluctantly go the easy route because the time and effort involved in developing more interesting concepts isn't worth it in comparison to the amount of items you get from the easy route. I've also played on tech servers where we agreed to work on a new concept but some players decide to just go and build a portal based farm anyways discouraging people from spending their time to design a new farm for items which we already have plenty of.