This is easy to see just by looking at bitcoin's year-over-year growth. Do we still see bitcoin giving 1000%, 100000% returns if someone invests in bitcoin these days? Did we see Bitcoin go 10x, 100x in the latest bull run? It is almost certain that those things are in the past and we will never have the chance to witness those wonders again. That alone shows that as bitcoin matures and its capitalization increases, its returns will diminish over time. But that's not necessarily a bad thing because the larger the capitalization, the more liquid and safer it is.
Yes, it's not possible to have those 1000% to 100000% returns again with Bitcoin and someone who understands the market knows that fact very well. I don't expect to see Bitcoin going 10x or even 2x easily even in this bull run because it won't be an easy thing to achieve. Now, Bitcoin isn't a low market cap asset it's already a pretty high market cap asset and that's why even thinking about getting 10x return faster with it within a few years is a sign of pure stupidity or day dreaming. And, when it grows more in market cap then it will surely become less volatile as compare to its current condition.