HIGHLY IMPORTANT TO NOTE: MY PROBLEM IS NOT WITH THE EXISTENCE OF VARIED CONTENT, BUT WITH THE MAINQUEST AND EARLY GAME CENTRICITY PUNISHING THE PLAYER WHO DOES NOT DO THE MAIN QUEST DESPITE THE GAME BEING INTENDED AS AN OPEN WORLD EXPERIENCE WITH MANY OPTIONS
Developers can use showcasing to trick unknowledgeable reviewers. My solution is finding and reading reviews by those who play open-world games as open-world games. You can tell what kind of player a reviewer is by reading his review and seeing how he plays. If how he plays isn't clear, then beware. If how he plays isn't how you would play, then beware.
Showcasing is a problem of game reviews, not of games. Getting rid of showcasing doesn't fix the problem of too few high-quality areas.
The evidence that Bethesda showcased Skyrim is weak at best. I find Meridia's dungeon and the East Empire Company Warehouse, among other places, more intriguing and more fun to explore than Bleak Falls Barrow. If you yourself built numerous places, some of those places would be more interesting and some would be less interesting. If you built quests, you would try to make each as entertaining as possible, so you just might choose to host them in the most interesting places available. An attitude of "let's impress reviewers in the first 20 hours" is not needed for putting more attention into areas visited early and often. Such results come naturally without it.