Braggadar: I hate <Insert platform>, but it's exclusively offering <insert game title>, which I want. BOOOO! EXCLUSIVES ARE BAD!
Seriously though, in some deep dark hole there is the same argument getting thrown around about GOG getting Diablo exclusively.
Well. The difference is that GOG works hard to find the rights of old games, make them work and all related stuff, hence it is only fair if they can profit from their own work for a bit before the same build is thrown elsewhere, as is the case of many old games on Steam as soon as the timed exclusivity expired.
Without GOG, many old games would be sold in an unusable state or not sold at all.
Epic just use Fortnite money to buy third party games like there is no tomorrow and lock them behind their... questionable service. Not even Valve ever went that low, and believe me if I say they have kept on digging since 2004.