Altcoins are important for one factor, it's ever-evolving and changing. Bitcoin's capabilities will only go so far, but there are various of top blockchains that are gaining ground in various of niche's and territories that Bitcoin could never reclaim. There will be a realization soon by all investors in crypto, that many altcoins are undervalued with respect to their network size, the underlying tech behind them and the overall value these blockchains offer to the real-world.
There are many altcoins that are still heavily overpriced, despite experiencing alt-time lows-vs BTC pairing and there are many more alts that are heavily under priced (for their integration, network and functioning as a business) that will soon be realized by all. This is why, if the next major alt-season comes, the reigning thought is many shitcoins will die out. This is somewhat true, because in the end, if there is money to be made, it will be made regardless of what the shitcoin looks like.
My encouragement to everyone, is patience and understand exactly why you're holding or have invested in your particular altcoin or shitcoin. It may ultimately be sound reasoning to cut your losses short on a particular coin and delve into an existing, functioning business and highly active team around their particular blockchain or protocol. Money is to be made on alts, the time is ever looming on us all. Bitcoin is the leader, but crypto does not end with Bitcoin, it only ever started with Bitcoin.