Can age based content ratings like ESRB or R18+ do anything to limit lootboxes in a legitimate capacity? AFAIK they're similar to PG-13 or R ratings for films. The guidelines are very broad and tend to not be enforced. Perhaps it is simply not feasible to do much to regulate lootboxes given current formats and internet protocols?
I doubt that they will completely eliminate minors from participating into games with loot boxes, same as some minors who visit casino websites (and even porn websites lol). But the fact that there is an ongoing bill with their Senate, I guess that this will give some companies the initiative to be more stringent with their games.
Again, while this move will not completely eliminate minors from purchasing loot boxes, this will actually lessen them in doing so. I just hope that the bill comes into fruition and becomes a self-executory law. This kind of move is what most countries should implement and create as well for the safety and well-being of minors.