I can think of a few reasons.

First, if we define "shitcoin" as only a cryptocurrency that was created to enrich its founders at the expense of the users, then yes, Monero is not a shitcoin. However, that's not the only criteria I use. If it also has a central individual or group in charge, then it's a shitcoin. And only Bitcoin fails to meet that requirement.

Second, a money is only as good as its assurances. Since the chain is opaque, I can't verify the current supply (though the total supply is infinite, just like fiat), so I have no assurance that Monero's monetary properties are what they claim to be. I'm required to trust that the developers haven't secretly created a lot of it for themselves that they'll dump on the market later. Bitcoin is all about "Don't trust, verify", but Monero is all about "Don't verify, trust".

Third, Monero is built to be 𝘪𝘯𝘵𝘦𝘳𝘯𝘢𝘭𝘭𝘺 private, but it can't affect anything outside its system. Very few people use Monero, so it has a very small anonymity set, which makes it really quite easy to circumvent its privacy, compared to Bitcoin. Chain analysis on Bitcoin is a pseudoscience anyway, but when you add millions of users, CoinJoins, Lightning, and physical bitcoin (OpenDimes, SatsCards, etc) to the mix, surveillance on Bitcoin in any kind of meaningful scale is simply impossible.