It’s only less secure in a rare circumstance that a bootloader compromise happens by theft or advanced malware. If you’re not doing stupid stuff on your phone you probably won’t get advanced malware on it, and most thieves probably don’t even know what a bootloader is, so IMO the security is good enough.
So the practical benefits of improved privacy and removal of bloatware etc are a much more significant benefit over stock android. I won’t use a phone with stock android at all after getting used to Lineage and Graphene