The senior engineer death spiral

Unfortunately, this is something you have to learn through experience and cannot be taught by someone else.

I've interviewed several great senior engineer candidates over the last few years, and then had to watch do this and walk themselves right out the door inside of 6 months. I've developed a marked preference for promoting internally, because you get longer to head this sort of thing off.

Incidentally, this sort of thing is why software engineering desperately needs some sort of formal levelling criteria and/or mentorship programs. It's really hard for senior folks to calibrate themselves against their rapidly shrinking peer group.

The best advice I can give on moving your career forward is to not try and get a promotion at your current job. Apply for better positions at other companies while you still have your current role. You'll have maximum leverage and unlimited time to choose the best possible option. Trying to claw your way up the ladder in a single company is the least efficient (and more often than not hopeless) strategy.

I’ve yet to decide if that’s what I actually want or if there is another solution out there. Is leaving the only real solution?

Instead, just communicate with your stakeholders asap. Chances are they already know the project is at risk, and they'll be amendable to either descoping or pushing back the deadline.

Also there isnt much above senior/lead engineer these days, there is no straight line career progression above that. You can try to get into architecture but thats mostly paperwork, or management which is mostly dealing with people.

If you want to call your own shots as an engineer the world is your oyster, start your own company and build it. There is not much worth "being in charge of" in corporate dev shops that I can see or would want to be a part of. Most of it is retread, make work including FAANG.

obviously, more senior ICs should be creating/defining/delivering their own work. But either way, alignment with director or TL seems like a good idea to reduce anxiety

I wish that I could travel back in time and tell my 25-year-old self this information.

This is probably an example of the Peter principle:

The Peter principle is a concept in management developed by Laurence J. Peter which observes that people in a hierarchy tend to rise to "a level of respective incompetence": employees are promoted based on their success in previous jobs until they reach a level at which they are no longer competent, as skills in one job do not necessarily translate to another.

https://en.wikipedia.org/wiki/Peter_principle

There's a huge amount of title inflation going on in the industry. We're now seeing the "Principal Engineer" title being given to people with 3 years of professional experience.

Unfortunately, this is simply not enough time to be very good at all, no matter how much raw talent you have. It takes a decade of experience just to know how to manage yourself effectively, let alone mentor others and lead large projects.

But I suppose the message, hard to read as it is, is something that some people need to hear. I've seen this first hand a few times, mostly in people who got promoted by working really hard and the more they got promoted the harder they felt like they must work to keep proving themselves. This often led into burnout.

I don't know; I don't really want to blame the people themselves or say that they're the ones responsible of their own condition. People, and I want to say technically minded people in particular, are each rather fallible when it comes to our own humanity and the psychology underneath. And so, I'd much rather see this same advise be targeted to managers and senior teammates: when you notice a colleague who seems to have gone in too deep, have a friendly chat. They might very well be blind to it, or trying to ignore it to push through just that one more time.