It's weird because a few years ago the idea of microtransactions was laughed at and reviled, but now they've permeated the industry and get a lot of defenders for various reasons...even though every time, they very clearly do what caused people to not want to see them become commonplace: alter the gameplay to suit the microtransactions. Mobile games are built around them, GTAO has the gameplay tacked on and hacked around with to suit them, and it's suffered dearly.
But hey, no content is technically locked behind a paywall so it's obviously completely fine. Also, GTAO is also free so you literally are not allowed to complain. Ah, GTAO defenders...
It's rather telling when people don't have much experience with other games.
A few years before that they were even seen as a good thing - f2p games with microtransactions for ideally cosmetics only, but a pass was also given to pay to speed up models. It was a pretty common opinion on PC, particularly with MMORPG's and other progression based online games. But as like you say, games started being developed around this. The base games became stripped of cool cosmetics and they were slapped on the store for as much as one quarter of the price of the actual game its self, or (as we've all seen with GTA:O) the games exp/money earning rates are abysmal and encourage you to pony up the real world dough.
It'll be interesting to see where the industry goes with post-launch monetisation if the microtransaction bubble as we know it pops. People know when they're getting fleeced and while they might not get fed up with it straight away, they will get fed up with it eventually. After that, is it a return to expansions? Sub fees? Something else?