Why would you ever think that? There are many fantastic pieces of media with utterly unlikable protagonists, and although many readers won’t shy away from disliking them and listing their many, many flaws, they won’t deny that the writing is good.
Take Walter White from Breaking Bad. He’s selfish, ego-driven, narcissistic, and that’s not even getting into his twisted relationship with Jesse. But it’s also highly regarded as one of the best TV series of all time in regards to its writing, directorship, acting, among many other things.
Or take Dexter Morgan from Dexter, who’s well-known for being emotionally detached, arrogantly viewing himself as morally superior to the people he murders, and a master manipulator. It would be interesting to see them face off, now that I think about it. But regardless.
One thing you have to remember is that just because a protagonist isn’t likeable, it doesn’t make the writing of them bad. In many cases, they usually have a reason for acting that way, and if the author doesn’t manage to create a believable transition for their character development, THEN it would be bad writing.
Or lazy, like introducing a split personality/evil twin that has been pulling the strings this entire time out of f**king nowhere like most of the Riverdale cast for several of their plot threads.
It’s also worth keeping in mind that just because the protagonist is the guy that’s front and center, that doesn’t necessarily mean that every member of your audience is going to respond identically to them.
There are side characters, and maybe even the antagonist that they would resonate better with, which is why it is paramount you don’t try to favour a particular character. I’m not saying you absolutely have to kill them off if enough people dislike them, but you will need to know when to end their arc and let other characters shine.
Or even let your worldbuilding help here in supporting your characters’ personalities. A past obscure piece of history that proved fundamental in their worldview; being raised a certain manner which develops other cultures in your fictional world, there are so many ways you can do it.
But don’t ever consider an unlikeable protagonist an indicator for a bad story; you just might end up missing out on some genuinely great stories.