There are a lot of roles that a main character plays in a book. They are the thread that pulls the the plot forward. They are the main actor in the climax of the book. And they are also the point of view that readers are getting the story from.
That means that having an unlikable main character is going to be a big deal for your readers. After all, who wants to listen to a jerk or an idiot tell then a story for four hours?
Beta readers and writing groups can easily tell you if your character is coming across is likable or interesting. As a general rule, the meaner the character is, the more competent they must be. People love Sherlock and Loki, who are absolutely terrible to other people (both have killed people) but are also brilliant and clever and one step ahead of everyone. On the other hand, people also like Anne of Green Gables, who pretty much screws up with everything she does, but is sweet and genuine and trying very hard to be good.
Maxing out either of these traits in the same direction is going to be a problem. If you have a mean character who is too incompetent or a nice character who is perfect at everything, those are going to cause you issues.
If your character is somewhere in the middle on both, then it's time to think about making them relatable. While it can be funny to watch a millionaire whine about sitting in business class, it's not going to be relatable to most people. It's not going to get them on your character's side. But all people have something in common with other people. So you (probably) don't need to change your main character, you just have to change the way you introduce them. Make your first couple of scenes a way to show readers that your main character has interesting skills, even if they aren't the world champion at anything. Make the first couple of chapters a place where your main character is going through something that your readers will sympathize with. And make your first couple of chapters a time where readers see the character around the people they care about, where they see them being a good friend, mother, father, brother, sister, pet-owner, neighbor, coworker, etc.
If you're having trouble figuring out how you've done at creating a main character, here is a fun test that will help you see if you've reached true character creation or if you're creating an alter ego or perfected being to act out your plots. The list goes over a lot of common red flags that might scare people off from your character before they've gotten a chance to know them. Having a few things from this list isn't bad. But if you start to hit an awful lot of them, it might be time to add some more realism to your character.