Not allowing persistent settings when not connected to an account IS questionable. As I said, I'm pretty sure you could do that before.
As to enabling subtitles by default, it is also questionable. The language for a given video can even seem kind of random as tycz said. I dunno if this change is made for the reason of being more "inclusive" (for deaf people for instance), which would go with all the woke stuff that most of those platforms promote. Don't get me wrong I'm all for making this available for them, but why by default?
Or if it is to maximize the number of viewers (which could also be a good reason for them) - to get viewers that don't understand the original language in a given video - except that translations are rarely available, or in languages you don't care about.
I don't see how it could be helpful for "most people" as golden_labels said. For some, maybe, in some cases. Why push it to everyone?
But as I said, the most irritating is that it can't be made a persistent setting anymore. Not if you are not connected to an account. And even if you are, it just keeps getting re-enabled for no apparent reason. It looks like the kind of thing Microsoft also does with Windows, so that's probably the new normal: constantly getting pushed with stuff you don't want, even when you said no.
As to it being easy to disable - it is on some platforms and not so much on others. For instance, on Firefox on a desktop OS, there is a subtitle icon that you get when you hover your mouse over the video, so it's just a click. But on mobile devices on which I use Opera, the player doesn't allow that. All you get is an icon for video settings, so you need to touch the video to get the settings icon, then touch the icon, which pops up a settings dialog, then there is a combo box list that you need to go through with all subtitles languages and get to "disabled", which is all the way up. Horrible.
The YT player has just kept getting worse anyway, and it's even worse on mobile platforms IMO.