The main RS3 game already seemed to have it's course firmly set towards pay to win / bonkers exp boosts in addition to the unpopular EOC update. As someone who has not played it since the EOC update, it is basically unrecognizable now.
I picked up RuneScape again in 2019 - initially it was the nostalgia that engaged me, but it was new content that hooked me back in to the point I am still currently playing OSRS. I think for a lot of current OSRS players, it is the difference between playing a game similar to the original vibe of RuneScape or not playing at all, and Jagex would have been dumb to leave that on the table once it was proven that old school as a concept could work.