No be only bitcoin, litecoin, Ethereum person go trade na abi other altcoins na crime there?
Liquidity is another reason coins are limited on fiat supported decentralized exchanges, but you can use ethereum based, Binance coin based etc decentralized exchanges like PancakeSwap, BinanceDex etc for exchanging other altcoins, the liquidity on this later decentralized exchanges are high, but not fiat based, just for coins and their respective tokens.
Also on centralized exchanges, only few coins are listed for p2p trading, just that people have the advantage to convert/trade some other coins to the coin that can be traded on p2p on the centralized exchange.
That means to say no where deh completely safe too be that na. If Centralised exchanges get disadvantages and Decentralised exchanges get their own disadvantages too so where we go run enter then na. The best thing na to just to deh deh careful be that.
The reason it is said that people should not use centralized exchanges is because people using it do not have full control over their own crypto assets on the exchanges, it is just as a warning which is true. But some people will still just make use of centralized and decentralized means in a way some certain huge amount of coins will not go beyond noncustododial wallets and decentralized exchanges while also still making use of centralized exchanges for tradings which are not possible on decentralized exchanges and using the opportunity to exchange coins to naira after making profit from trading.