I think the successful altcoins will be the specialized coins. These coins are created with clear differentiator and purpose. I don't think ETH will be successful. It's super bloated and has even more vague use cases than bitcoin. Dogecoin is a good example. The idea is silly but it has a clear differentiator. All other limited supply/store-of-value coins will eventually be chewed up by Bitcoin.
If you cross out limited supply, I think there's opportunity. I'm working on one:
https://bitflate.org/.
It's kind of ironic when you criticise ETH for vague use case but then promote your own coin which has no use case mentioned?
Bitcoin is a Store of Value. Bitflate's use case is for transaction. It's a digital native stablecoin. It may sound weird. But I think it could work. I think inflation discourage hodl. People have incentive to spend this coin. Its price would fluctuate but it is not as volatile as bitcoin. Existing stablecoins require a centralized bank ledger. Bitflate is decentralized like Bitcoin. This feature will attract business adoption. I think Bitflate will be a somewhat stablecoin. But being digital native is a good trade off.
Money comes in duality: inflationary and deflationary. Bitcoin exists because it has inflationary fiat currencies. I think an inflationary digital native currency is the missing piece in crypto space.