My 2 cents: if you have a good relationship with your manager and you think they are a good manager I’d stay, but I’d tell them that I’m stressed with the situation and feel that we’ve lost a lot of the know how while I’m still new - they should understand and support you, and defend you if criticism comes in. I’d also do my best to increase knowledge to fill the gap and angle for seniority - it’s actually (probably) a net win in your situation unless the current state is a shambles.

Of course it might not be the current great resignation behind this, I’d also try to figure out if something else is going on.. is there a culture problem, is the manager no good etc..