It does not eliminate anything. Let's take the longsword, for instance.
1. Without Flex Mastery (let's say a ranger, paladin, bard, or a fighter that does not select the "flex/longsword" Mastery option), versatile lets you use the longsword in one hand for 1d8 damage, or two hands for 1d10 damage. When does this happen? Perhaps when shieldless Rangers and Fighters drop their ranged weapon to swing their sword with both hands for some extra oomph? Or whenever a shield-bearing combatant cannot use their shield? Any which way you slice it, it's fine. This still works. How many people actually plan to use 2-hands with their longsword as their primary way to attack? I think it's only to get an extra bit of oomph when you have nothing else to do with your off hand.
2. However, with Flex Mastery (let's say a fighter chooses this mastery), versatile lets you deal 1d10 damage while your off-hand is busy, like when you use a shield, or are hanging from a rope, or want to be able to make unarmed strikes to grapple your opponent. Yes, "Versatile" does effectively become a keyword that enables you to do all those things, but your damage is as good as many 2-hand weapons, opening up tactical options without giving up damage. For instance, if a high level Fighter can implement more than one mastery on the longsword, they can choose between Flex and whatever that other Mastery option is from attack to attack. And if the designers decide to create an option that allows characters to wield 2 non-light weapons for two-weapon fighting, there are so many people who would love to dual-wield 2 longswords for 1d10 damage each. I'd do it at least once.
Sure it's not super powerful, but it is fine. I can see a place for it. That said, if they drop it or replace it as part of the playtest process, I won't get too bent out of shape over it.