Omnipresent POV has really fallen out of favour, and in only exceptional cases is it used effectively basically because of the reasons you have given. It is very hard to hold the reader at arm's reach from the characters that most of them are reading for, and only the exceptional examples of the genre can do it. I know as a college student that's waving a red flag and saying I bet you can't do it, and if you want to prove me wrong, all you'll be doing is practising and so we both win.

You're asking someone to put ten bucks after all their expenses and 4-5 hours when there isn't enough time to do anything to read your book. Sure, whether they read the first book doesn't matter; they still bought it and you made money, but that opinion only works if you're looking at readers as hogs to be slaughtered and not sheep to be sheered...I mean, become involved in a long time business agreement where you write what they like and they keep buying (and reading) it. Most are reading to get behind a character, whether a major or a secondary, and Omni is an ensemble caset whether you like it or not.

There's also the issue of dramatic irony that goes right out the window. If you can be in any head, and you're not in the head that knows the thing, if that character keeps silent while the thing that everyone needs to know before the ice giant is about to break down the door and kill everyone, the reader can feel cheated. There are a lot of things people can be dong with their money, but most importantly their time. And if your book has a great premise, interesting plot, but one character for them to root for, the whole thing can fizzle out.

Things fall out of favour for a reason. If you produce the best omni POV book in the world, you're still only going to sell it to the limited market who enjoys the world and not the characters in them, and from their, you're only going to sell to those who finished it and liked it. For an early book, if you're goal is to be published, to limit its market like that is a bit self-defeating.

Still, write what you like. If you go limited 3rd but do multiple POVs, you run into the same problem from the character standpoint. Setting up the beginning to get your reader to start cheering for your character is a hard enough ask to do it once. Setting up multiple POVs you run the risk of a reader loving character A, not liking character B, and when you introduce character C, at best the reader will only get 1/3 of their favourite character. Or worse, they might really have liked Character B, but never get through Character's A intro to even get to know him.

I was taught at a young age to never draw to an inside straight. Cutting your chances in half of pulling the right card is hard enough, you're taking more than one chance with an omni or multiple POV. If you're going to do it, just do it the best way you can, but for tips and tricks, try writing it as a later novel once you get writing a novel a bit more down, then branch off to write your opus.