You can always try starting something up, but it is honestly pretty difficult to beat the cost/benefit of just getting a promotion!
I used to build a lot of projects after (and before) work. I had over 100 projects before I built my first successful side hustle (which is now my sole income, > $2MM).
I can't imagine going back to working for a company. I was an engineering manager and working my way up the company, but it's not for me.
The answer to whether you should climb the ladder or start a side hustle depends on what you want for yourself and where you want to be in few years. You are most likely to make good money in a job than a side hustle. So if the goal is just to make money, I would say go for a job for now. That doesn't stop you from doing some side projects of course but then it comes down to how bad you want to do it.
Unless you have the entrepreneurial itch so bad that you just can't do anything else, I suggest you get another job and at least stay at one place for 3-4 years and gain real deep experience. If you keep job hopping, you wont be very valuable after another 2-3 years.
Just my 2 cents as someone with 20+ years of experience in the industry who runs his own thing.