it technically uses an altcoin that is pegged to BTC---there is a difference.
no layer 2 protocol can ever provide the same security guarantees that bitcoin does. i think that's why interest in them has traditionally been lacking.
Whatever it is, it's still pegged to bitcoin, has no premine, is immutable, is not as centralized and is much safer compared to the alternative such as ethereum.
The only reason why the interest in RSK is not as much as ETH is because you can't pump and dump it like you pump and dump ETH so there isn't any profit to be made there, and also the hype of the ETH platform means you can easily create the shittest and most useless token and still dump it on idiots and make money whereas if you do that on RSK nobody would even hear about it let alone anyone buying that shittoken.
ETH is still by far the king of all altcoins because it is definitely something profitable to hold when hypes happen, it is the second biggest coin so when bitcoin stops eth starts to grow. Think about it this way, if bitcoin is loved so much and everyone gets it, the moment they start to look for something else? They look at ETH and that is why nothing else can ever pass it.
It doesn't matter if the tech is better, it doesn't matter if there is a better feature or a code, it doesn't matter whatever other coins do better, you think bitcoin is the top coin because it has the best blockchain? Obviously bitcoin is one of the worst coins technically speaking, there are so many coins which are hundred times better than bitcoin, but bitcoin still leads them, because it has a larger community that trusts it, which is why you should focus on ETH being second, not ETH code.