If you buy coins with strong fundamentals, you reduce the risk of getting stuck with shit coins. If you just buy whatever is pumping, the danger is much greater. And diversifying makes it possible to balance the risk, and focus on gaining more than you loose. There will almost always be some losses, you just need to gain more...
Everyone can’t make 20% gains every day. I’m not convinced that we have hit the absolute bottom with alts, at least when talking price relative to bitcoin. But I don’t see much of a downside either. Buying in now will get you coin at a bargain price, but it can still take a while before alt season hits. So, don’t buy and expect instant takeoff.