That you gotta now disable all other adblocking setups on YT for uBlock Origin to have the best chance of working. Even PrivacyBadger will interfere now. This includes turning off Firefox's Enhanced Tracking Protection on Youtube (the little shield icon in the address bar - click it for options. It's per-site, so just for YT, don't worry.)
UPDATED: @plumpan has linked a great chost about other, specifically off-site not-on-Youtube ways of getting around this mess if uBlock Origin meets its end on the battlefield - it's called FreeTube, it's in the linked chost above, go check it out!
I've just been running uBlock Origin (and YTEnhancer+SponsorBlock, but those are different), keeping it up-to-date, and it's been flawless so far.
If you want it to work properly and you've not got it autoupdating, you really need to follow these steps properly and fully. Yes, that does mean disabling ALL your addons, removing ANY custom filters for Youtube, and basically starting from scratch with a clean, recent copy of uBlock Origin.
Right now, Youtube is directly trying to counter uBlock Origin in some manner. @mocha has a great little backup userscript to automatically embed the video you want to watch into an iframe, which is the other, manual way to watch the video. Excellent to have as a backup.
At this point? Don't be afraid to pirate your favourite videos. Seriously. Download them if you want. Use something like YT-DLP to rip vids where possible.
It might be important, soon. Just saying.
More just a personal observation, but YT can't win this. I mean that. I don't believe I'm being naive about it, either. There's no tech or method that YT can employ, as far as I'm aware, to lock down their service without completely preventing public access, which will, invariably, kill the site.
You might think they can? But they can't. People have already (as above), and will continue to find ways to watch videos uninterrupted and ad-free, no matter the initial inconvenience. And they will automate that process so it's as if nothing changed. It's a losing war, and it's Youtube's fault for not finding other, better monetization schemes than fucking advertising. They think they're going to win by attrition and frustration, they think that throwing more and more ad-dollars at the problem will make it go away, but it's literally not possible. The moment they stop escalating the arms-race, adblockers will win. So they'll have to lock the site down COMPLETELY. Paywall it all. And that'll be the death of it.
EVEN IF they completely paywall Youtube - no free content at all, no public account-less browsing, must be logged in AND paying to see ANY content (which would be a death sentence for something the size of Youtube, FYI - it cannot self-sustain on solely the reduced percentage of paying viewers that would remain).
EVEN IF they did this, they'd still fail.
Why?
Because it only takes a scant percent of people paying for a subscription to bulk-rip the content and make it available online, elsewhere. Not enough profit for them to survive, because they will have literally shut themselves off from the public, removing any potential passive income they could have earned in good will by having ads that aren't dogshit. But no, they don't care about that. They only care about MONEY. Which is why they can fucking rot!
The process will be slower and less convenient, sure, but by this point in the process, SO MANY large creators will leave Youtube for any other option that doesn't lock out the free public, that it won't matter. Youtube will lose its position as THE main video website, and something else will eventually come along to take its place.
Keep spreading the word. Tell your friends and family to install uBlock Origin, and maybe support the devs instead of paying a YT subscription. Install it for them if they're not too tech-savvy. It can't be worse than fucking advertisements.
