I dont think you can objectively look at this franchise and say Loomis isnt to blame for where its at. He is going to be here, all we can do is hope he can fix it. But this roster, starters and depth, cap situation, etc is all Loomis' doing.
Loomis picks the HC. But even then, I would imagine that they treat that like the draft where they come up with a consensus with Loomis, Ireland, etc. with Loomis having the final say. Loomis is responsible for picking the HC, and he's responsible for getting the HC the players he wants. And he's very good at that.
But here's the reality of the NFL. There are a few top teams. And everyone else will be looking for a new HC every 3 years or so till they can break into the top 5 or so NFL teams. That's not easy to do. So the most likely scenario, whether they pick an offensive guy, or a defensive guy is that they will be picking a new HC in another 3 years, because that's just how the NFL works. And part of that is just being at the right place and the right time, like with Payton and Drew.
Nobody would argue that the Steelers aren't a top organization or that Tomlin isn't a good HC, yet there are rumors of the Steelers firing one of the best coaches in the NFL. Good QBs aren't easy to find. Unfortunately for the Saints, it's not the right time and place unless Rattler develops into something special.