Then they would have been around the playoffs but not real contenders through the end of the Smith deal, same as they were.
A top QB is the most valuable thing in the sport, the 2nd most is a good QB on a rookie deal, if you don't have one you take shots until you do.
Also, QBs who don't work out (at all) is usually a product of bad scouting and bad coaching. Mahomes didn't have to be MAHOMES to give them a better chance to win, just Alex Smith but cheaper, or ideally better than Alex Smith.
Sure very few shots will work out as well as that one did, but it's the kind of move you make if you want to win. PHI is another good example without the trade up. They knew their QB situation wouldn't cut it so they kept taking shots.
Edit- now, part of this is philosophy, I am looking at it from the perspective that you want to win a ring. Not always true, some GMs are just looking to not get fired, some owners are just looking to win 8-10 games. In that case they choose to settle in for teams they know aren't going to win a title, but will be... okay.