Depends on the game but what comes to mind for me is the NBA 2K series. They started stretching out the game to add grind and then added the microtransactions to then skip the grind they purposefully added to the game. Then to take it even further they started removing features from the offline game so you had to play online, where they push you towards spending money, to play the fully featured game that you used to get out of the box for your 60 bucks.
I'll counter that with an example where I think the mtx works or used to before the new lootboxes, Lord of the Rings Online. As a MMO is was always kind of grindy and always had deeds where you had to kill hundreds of something to finish but when they went free to play they added deed accelerators that allow you to finish those objectives in half the time. Add to that it's very easy to earn decent amounts of cash shop currency in game and both the lootboxen and keys to open them were landscape drops and deed rewards. Here the game plays almost exactly as it did before even if you don't spend a dime and spending money lets you speed things up from normal as the devs didn't slow the base game down to push you to spend as they did with NBA 2K.
So, I guess the difference is if it feels exploitative