I never had help from senior engineers. No mentoring whatsoever. I learned by doing, making my own mistakes, learning from them. So it’s not a requirement to have good mentors. Although they may shorten the journey.

Having an insatiable drive to learn is the only requirement! Keep reading, keep doing.

Would I change it if I could? No. I think I’ve built up a strong will and understanding of the craft. The opinions I have are self formed from doing. I like that.

I at least tried to reverse the situation by doing whatever I could to help mentor my juniors over the years. But it must be said: just because someone is senior it doesn’t mean they’re good. You can easily end up learning dogmatic bullshit that takes years to shake off.

So I always say to juniors “take my words with a pinch of salt. I might be wrong. You need to find out what you believe on your own. Don’t just rely on my words alone”.

In your situation you should have an honest and frank discussion with your boss. Tell them you're feeling a bit out of your depth. Explain that you think you need more senior heads to help guide the project. He/she'll either take it seriously, or not. If not, leave and find somewhere else to work. If you don't have this conversation then any failure will be yours alone. If you do have the conversation, then you've moved the ownership of future issues to your boss.

Also, working in a company where the product is what you write is the place where you'll learn the most.