Bitcoins are for long term only and altcoins are for short term trades.
It depends on the situation. In my opinion, Bitcoin or altcoins can be short-term or long-term.
If you only target small profits, you can use Bitcoin for a short-term holding. Just imagine when you bought BTC at $17k, you can get profits now since it is already $23k+. But if you target bigger profits, you can hold for a longer time, probably until the bullrun season. Well, it is also applied on altcoins, but it is for the top altcoins only.
People choosing Altcoins should be familiar with the character of each altcoin, and it is safer to be with the top altcoins and developments that are clear for the future. Don't just choose altcoins based on other people's stories.
Of course, people are brave to invest in altcoins because they know well altcoins.
I don't think top altcoins are safe enough, you must know what is happening with XRP. Although it is one of the top altcoins, the price decreased much because of the case with SEC.