Sounds like you've already made up your mind so don't overthink it. You'll most likely never see this person ever again and even if you did, you wouldn't want

Sounds like you've already made up your mind so don't overthink it. You'll most likely never see this person ever again and even if you did, you wouldn't want to work with/for them so why would it matter? Best advice would be to exit gracefully, no need to "burn a bridge". If you want to play it really safe and keep your options open, be diplomatic about it and, once you secure a new role, say you found something more aligned with your long term career goals / better pay / enticing product etc and you decided to move on but are happy to stay in touch.