These are sites which aggregate the data from exchanges. You dont "find" coins there. If you are looking to search out the number of cryptocurrencies in all there are, then use them, or for market date. But dont use them for new coins to invest in.

That things need more research from your side. Whether the team has anything worth developing or not and if at all the market into which they are divulging is worth putting money in.

Just note that 99% of the coins are not so, because if they were so then every crypto hodler would become a millionaire. Just like every penny stock hodler is rather broke more than rich, it is similar with crypto.