My experience as an Android developer is that samsung phones are garbage.

The ones I tested perform so much worse than same generation Google devices that it feels like a joke.

Samsung also does freaky stuff to AOSP, like making some random fields static, leading to some nice samsung bugs.

As far as the OS features and apps, I don't really expect anything better from them. Think of a feature, Samsung has probably already implemented it. It is probably going to be clunky and badly thought out but it will be there.

Sometimes it leads to interesting things though, like larger phones.

There are other shitty OEMs, but since Samsung has such large sales, it makes them all the more annoying to deal with.