So, here are some more mainlines:
Condom variation? Far from it. Fedoseev has played 2.Be2 many times. And he is not alone- you can add a few GM's to the list: Igor Kovalenko, Gawain Jones, Alex Lenderman, Kirill Alekseenko...
Now, try to find some theory on the "mainline" 2.Be2. You can't? No problem, there isn't any.
OK, now you can happily play your mainline. Just don't complain if the opponent cheats, and deviates from the book at move six or so- and you lose, because all you know about what you play are.... errr, mainlines.
That's not to say one should automatically play mainlines but as far as anything else I've read, it's common sense to play the "best" move methinks. At any level.
Yeah it's subjective. But if your goal is to improve your game, not play like a GM, do what THEY did. Study mainlines first. Shortcuts will guarantee some short term success. Building a foundation always guarantees advancement from one level to another.