[ruskyhacker]

I'm not a career dev, but I have inherited teams and projects before that were a huge mess...

This isn't going to come off nicely, but your assumption that it needs a full rewrite, is in my eyes a bigger problem than the current mess itself.

The "very junior" devs who are "resistant" to change are potentially like that in your view for a reason. Because of the cluster they deal with I suspect the resistance is more they spend most of their time doing it XYZ way because that's the way they know how to get it done without it taking even more time.

What it sounds like to me is that this business could utilize someone at the table who can can understand the past, current, and future business - and can tie those requirements in with the current environment with perhaps "modernizing" mixed in there.