"TikTok does not have the same diversity of content as YouTube."

Maybe this is true but it is also easy to get the impression because of algorithmic differences.

I think YouTube quite aggressively tries to find a global optimum for your viewing preferences and for that constantly throws a certain fraction of random content at you to test if you like it. At the same time there is high inertia for active engagement to influence your feed.

TikTok is completely different. Once you are locked into your niche it tries to keep you engaged there as much as possible but never strays into other niches by itself. If you actively search for content outside your niche it is quick to adapt.

So, if you are just a lurker on TikTok it is very easy to get the impression that content diversity is low there.