To be honest, not all cryptocurrencies are worth being held for the long term and most of them are extremely volatile and unpredictable and aren't suitable for this which is the reason why altcoins are generally used just for short or medium-term trading and not for long-term holding like Bitcoin. There are only a few altcoins that can be trusted to be held for a long time, ETH is one example of that which is the second largest and most successful cryptocurrency in the market.
It is also not necessary for a person to just do one of the two as one can always do both holding and trading since it isn't that difficult to learn the necessary trading practices and get into trading while you are already holding some of your assets like Bitcoin and ETH or a few more altcoins that you think have the potential to provide good returns in the long run.
Not all cryptocurrencies are safe to be hold for long time, which is true, but this is not a result of their volatility, because almost all cryptocurrencies are volatile in nature, unless for those called stable coins. Bitcoin is volatile, yet it's safe to be hold for long and has proven its self as a long-time-investment. When it comes to safe-to-be-hold, which should look at the coin-use-case. I mean, what they can be use for and not just all the hype they get from whoever is promoting them.
Most Altcoins, especially those Meme-Tokens, are not here to stay for long. They are short-time-projects, as I see most of them, and I will advise anyone, who wants to invest in such coins, to be careful and don't consider holding them for years without going to check up on them, before they end up losing all at once, just like those, who choose to invest in NFT, are crying out loud this period.