Most altcoin won't survive in the long run, but we shouldn't lump them all together. ETH has been around since 2015, while LTC, XRP, and XMR have been around since around 2011-2012, and many other altcoin will continue to survive and grow alongside Bitcoin.
Well, out of the altcoins you listed, LTC probably isn’t the best example. Yes, this alt is still hanging in there, but as a long-term investment, it’s a pretty boring asset, since it hasn’t really been eager to follow BTC’s lead over the past few years. Specifically, when BTC was hitting new highs and trading above $125K, LTC didn’t really stand out during that period.
Yes, you may be right. Its not just ETH, some other altcoin are still hanging around, but they are no longer attractive investment.
However, I think it's unfair to treat all altcoin as the same. There are still some altcoin and there will be more in the future, that are worth investing in for the long term as the market matures.
We should hope the crypto industry continues to mature and that more worthwhile project emerge, rather than focusing only on Bitcoin and dismissing the rest of the market.