All smart contract platform projects are worth investing in long term. because in the future smart contracts will become a much-needed thing. there will be many companies integrating their services with blockchain. Therefore, a smart contract is the most needed thing. that's why buying eth, bnb, DOT, ADA, TRX, EOS, and other smart contract projects will be very profitable.
Right, although not all the smart contract based altcoins are good though. Most of the projects coming up are either made on another platform like Erc-20, Trc-20,etc or they bring their own blockchain. Not all are worth investing, Solana was a good coin people missed and I guess more such projects are coming but because of the bear run, it's hard to pick them.
When it is too hard for finding a right coin at right time to invest with, I guess it is always a good and safer practice to go with only bitcoin investments so that we can focus only on a right time to grab opportunities rather than finding the right coins and then missing them out.