I wonder what the threshold will be for YouTube to start losing a critical amount of relevance.
YouTube is way, way less interesting than it even was just 5 years ago. Discoverability is in the toilet, and being discoverable usually means a high level of investment on the part of creators. Everyone is playing it very safe as a result, and your average YouTube video today is remeniscent of where cable television was just before streaming began drinking it's milkshake.
Being aggressive against Invidious, youtube-dl, and ad blockers won't help them in the long term. Maybe they are covering their tracks for something, but even so, they will lose relevance. For many, their content isn't worth paying for, and even when it is, some hesitate to give money to a company that is likely to pull the rug from underneath them.
The best thing YouTube can do right now is get rid of their current C-level and replace them with people who are either actually YouTube enthusiasts or creators themselves. Corporate bozos always bring down companies that have revenue models based on creativity. That isn't to say YouTube will go extinct, but it's second life may be a rebranding and only allowing content from established businesses, and being of little relevance.
When it comes to Invidious, YouTube wouldn't have to do much to keep people in their own frontend. Their search function is complete bullshit today, and that would be an extremely easy fix. They can stop bubbling CNN, Fox News, MSNBC and co. to the top if you type in certain keywords. (obviously they will never do this though) They can improve the filtering of searches. They could fix the bugs with the queue and stop introducing new ones all the time.