Your fears concerned with longtime investments in alts are understandable. Most of alts are not as reliable as BTC and are bad for longtime investments as they can dump and even scam. However I think that there are some alts that are good for longtime investments. I’m talking now about ETH and BNB. This two alts seems for me really good because first one (ETH) has a huge platform with a lot of great projects based on it and the second one (BNB) is the main alt of the most popular nowadays cryptomarket exchange named Binance.
The fact that more users are now using the Binance Smart Chain network as an alternative network due to Ethereum's high gas fees, we can assume already that BNB might also have the same journey as ETH. The use-case of that coin is so vast that even simple staking can do on their platform Binance.
Binance also has lots of offers that users can do aside from learning how to trade. They are doing a good job making Binance the most reputable exchange today and I think no exchange or trading platform that can beat them for the next 4-5 years.