I joined crypto in 2017 and until now I still find it difficult to find or choose which project I should hold for a long time and it is true that the safest point is to keep your assets in the top 20 coinmarketcap, at least the project already has a very clear roadmap and team.
But that will not bring you a good profit. Many newbies don't abide by that rule because they are too immature, with not enough skill and knowledge to venture out top altcoin on CMC so usually failed in their investment.