If you're bootstrapping, be a cockroach - not a unicorn. I would not have been able to run Loki.ai if it was in a $100M+/year industry. Large markets attract VC-funded competitors and large companies. The only way it works is if you choose a market that is large enough for a solo founder or small team to make a comfortable living, but is small enough to not matter to tech-giants or to VCs.