They're not too good to be true. it's just the people making those kinds of returns aren't taking retail investment.
For example in crypto, market makers are commonly making 100% return. You haven't heard of these firms and they aren't interested in your money.
Market makers usually do quite well for themselves, but are capacity constrained: they can earn stellar returns on tens of millions of capital, but maybe not hundreds of millions or billions. You probably haven't heard of most of these firms and they would prefer to keep it that way.
of course if you want a public example, look at RenTec. They are unique in generating eye popping returns with such a large amount of capital. This is extremely uncommon. However generating comparable returns on 500-1000x less capital is significantly more common. These returns often don't compound tho, as they are severely capacity constrained.
