We regret about missing Bitcoin, then about XRP then about Ethereum then Doge then Shiba then Pepe (these are some top of my head and from what I've come across in my crypto term).
Point being there are always new opportunities and dwelling on regrets is futile.
Well, personally I don't have any regrets on missing out on any of these mentioned coins because I'm not really a fan of altcoins and I've only gained a few times with altcoins and I don't think the risk is worth it and the only altclin oj my list of holding is ethereum because I see it next to bitcoin .
Bitcoin actually remains the best to me and definitely I can't deny this and maybe I'm not yet ready to dive into the altcoins industry but I think I wouldn't hesitate to give it a trial if I get some funds I'm willing to risk trying them.