What is stopping you from deciding to just not trader-flip on flea? [Discussion]

I genuinely don't mean to come across as a hater here. As a (semi)-casual player I have a really hard time understanding the big issue with making Flea easy to access, including by selling trader and non-FIR items. I've seen a lot of posts since Flea opened complaining that they were able to flip X million into XX million in so-and-so minutes or hours. This is often used in the context of wanting to make the Flea harder to access or in other ways less impactful for the gameplay.

I'll give my own opinion on the matter directly below, but i'd genuinely appreciate comments explaining why this is wrong or what part of the picture i'm missing.

In my opinion, Flea is the single most important "catch-up" mechanic for timmies and casuals. And i'm quite struggling to see why this should be ruined, because some players choose to exploit it and ruin their own game experience. I mean, what's stopping you from just not trader flipping or just not selling non-fir items? That way, I can continue to scrape by and turn a meagre profit by selling everything I can. And those more skilled can just choose not to trader-flip millions and make the game pointless for themselves.

However, i recognize that there seems to be a lot of players who very intensely are of a different opinion. This makes me think I must be missing something.

Those out there who are of this opinion, would you care to explain (constructively, please) why this is an issue for you? I'd genuinely like to try and understand, so let's skip the crying and hating pls.

Edit: Having thought about it for about two more minutes, I've come to the conclusion that trader flipping is probably worse than being able to sell non-fir items. So, if your opinion is different of the two - i.e., that flipping should be removed but non-fir should otherwise stay, I'd love to hear that too.