The paint needs time to outgas in order to finish curing. Waxing will prevent that and the paint will never fully harden. It will scratch much easier from there on.
There are a couple of sealants that *claim* to be safe for new paint, such a FK1 2180 which claims to allow outgassing. I'm not in a position to validate that claim and most everyone around here is wary of that sort of thing. There have been a number of people here griping about paint that gets swirls if you look at it funny after a repaint and it pretty much always turns out that it was waxed way too soon. And don't listen to the dealer if they say they baked the paint so it's OK to wax, that just "kick starts" the curing process, probably by a matter of hours, not weeks or months.
I have been wondering, might it be possible to do a full chemical decontamination to fully remove wax and allow paint to finish outgassing? It would probably take someone willing (or desperate enough) to try it.
As for not feeling like you can wait 90 days to wax, trust me I can fully empathize. I don't even want to say how many partial or full repaints I've had just in the past year.
Edit: Forgot a couple standard things that are mentioned every time this topic comes up. To give the paint a little protection that's safe, use something like Meguiars #5 glaze. Glazes are usually safe and that one is made specifically for new paint.
Also, all of this stuff only applies to repaints, NOT to new cars with factory paint. Factories use different paint formulations and techniques so it's safe to wax new cars right away.