He's also 28 years old and has his entire career ahead of him still. With how much modern medicine has allowed athletes to extend their careers, I wouldn't be surprised if Mahomes plays until he's 44 or 45. He could easily win another 5 or 6 rings in that time frame, which means he would also beat Brady's 35 playoff win record. So I don't think drawing comparisons is that far fetched. A little early? I think so, but only because he hasn't won anywhere near as many rings as Brady or had as many SB appearances. But he'll get there in due time.
As much as I despise Mahomes, I can't deny the guy has a God given talent. If he would just quit being a little bitch every time he gets hit (and stop putting himself in unsafe situations, ala the helmet hit he took against the Dolphins), I'd probably have more respect for him.