There will never be a real competitor to YouTube

That sounds reasonable but you're thinking way too small. Lets not forget that Tiktok is already more popular than YouTube with a very, very large chunk of younger people, for example.

But besides that, let's not forget that absolute giants in the business have been toppled. Look at Yahoo! as one example. Hell, even entire countries can fall within a few decades, whole empires.

So, assuming that there will never be a decent YouTube competitor is a very limited way of looking at it. Who's to say Google will still exist in any meaningful market leading way in 20 years?

Sure they're big now, but what if the entire face of the internet and how we use it and what we want fundamentally changes (say with the addition of highly advanced AI that brings changes we can't even predict right now).

There will absolutely one day be a service that can rival YouTube and eventually replace them, it's the same with every product from every business, it's the circle of life I suppose. But whether that will happen within the next 5 years, or 15, or 30, only time can tell :-D

Never say never, though!