Many ways, but the most egregious is that it just randomly makes its own decisions about what the settings should be. I almost always watch YouTube on my LG TV (I'm aware that I can side load other options, but I don't want to do that kind of thing at least until my warranty expires). I nearly exclusively watch it with subtitles on, yet every time I launch the app, I have to re-enable them in the first video I play. I have found no option for that setting to persist between sessions.

Commercials usually have no subtitles (which is okay, I guess, but weird) or, when they do, they're messed up (for example, often the commercial subtitle will often be mostly off the screen to the top left and only show the last few words).

Commercials will often disable subtitles for the primary video until I re-enable them.

Switching between videos will often change the language of the subtitle from English (the only language I can fluently read) to Korean or Russian (neither of which I can read or speak at all) even though I've never chosen either of those options myself. This is the case regardless of whether English subtitles are available.

Often subtitles, English or otherwise, are completely unavailable, even though YouTube can auto transcribe things. This would be more acceptable to me on brand new videos, but I've seen it on videos of all ages.

Sometimes (though not frequently) I will start watching a video with subtitles until the first ad, then after the ad, the option for subtitles is unavailable. Even if I rewind to the part I already watched with subtitles, YouTube will proclaim ignorance. This is similar to an earlier point, but I forgot to mention it while I was typing that.

These are all the grievances I can think of at the moment, but I'm sure there are others. Apologies for any typos; my phone's keyboard has really been working against me today.

edit: It messes up every multi digit number (I haven't noticed whether it does single digit). For example, 2,000 becomes 22,000 and 20,000 becomes 200,000. I choose to watch with subtitles, but if you were actually in need of them there would likely be a lot of confusion, especially on scientific or mathematical videos.