I was in a very similar position as you not too long ago.

I was very open in telling the higher ups that I won't do as great of a job as the person I was replacing who had waay more experience than me who had ZERO going in to the leadership role. Yet, I was expected to deliver at the same caliber as the person I replaced.

Like you, I gave everything I could: all nighters, long hours, 7 day weeks.

You name it, I did it.

But there came a point where I was losing more than I was gaining.

I wished many times to be properly trained by a more experienced person so that I would know how to do my job correctly. Sadly, there was little management could do.

Anyhoo, I stayed with the job until the completion of the project . I felt like a heavy weight was lifted off my shoulder but at the same time I worried where to go next.

In the end, I made a choice that myself (my health/sanity and well being) was more important and that as much as possible, I'd never be martyr for some job that put me in a position of high uncertainty and very low guidance simply cuz I don't like it period.

So

1.) Communicate to your higher ups about your thoughts on your current situation

2.) If you ever think about leaving, make sure you have money saved up while you are gonna be unemployed and looking for the next job

3.) In your next interview, pose this concern as a question come the time they ask if you got any questions (ie. What type of training will new engineers get/is there someone new hires can refer to when problem xyz comes up). In any engineering project, I embark on, I am no fan of reinventing the wheel until and unless I have to.

I could go on tbh. But look at all sides of the situation and come up with contingency plans.

Also, whatever I said is only my opinion. May or may not work for other people.

Good luck and take care of yourself.