If a new incumbent can raise some money, offer creators some money and a path to a higher cut than their competitors, they can win big.
A video sharing website is not a social media platform, it's a streaming platform. The real competitors to YouTube are not PeerTube or whatever, it's Netflix and HBO.
This is why Nebula also managed to find a niche and be relatively successful: the issue is not ads or a monthly subscription or something, the only problem is: people want to watch high-quality content. Find a way to get them high-quality content. If you cannot do that, everything else is meaningless. In Nebula's case, even a few high-profile YouTubers in the same niche uploading exclusives on a platform is better than a thousand nobodies uploading low effort content.