Interesting point I think is being overlooked here is the reaping. Over all, just allowing heelhooks isn't that big a deal. But allowing reaping opens up a lot of different control positions that you wouldn't have otherwise. Even the recent video from Gordon Ryan on the matter, he also pointed out Heelhooks aren't that different and most of the big differences he mentioned we're the control positions.

At the end of the day, if you're a brown or black belt, doing no gi comps, and you're not learning leg locks and their defenses..... I don't know what to even say

It's not about learn how to defend a simple straight or toe hold lock. Some No Gi competitors became specialists on the leg lock game and they are reaping knees badly. Many people still don't realize how much the leg lock game have improved over the last years. We had three world heavy weight champions being submitted by a talented but much lighter opponent, in the last ADCC. You have to be prepared to defend leglocks in a fast manner, otherwise you will get dramatically hurt. A competition ,match and a regular roll in the academy are completely different things, in a competition people will give 100% to defeat you. If are not used to compete and already hold a higher belt, start by GI competitions, the things will get more exciting but kind of dangerous, in NO GI competitions.