It's impossible (and futile) to convince someone of anything unless it aligns with their goals.
Equally, advice from people who did things and met _their_ goals will not necessarily be helpful if your goals are different to theirs.
To meet your goals, open sourcing may not be the right thing to do.
So I think you need to reword your question before you will get a useful answer to your situation.
The place I tell people to start their own learning journey w.r.t this is https://coss.media
I've worked with companies who have gone to far in either direction. It's really more involved than an online forum can provide to answer your question.
Watch the interview between JJ and Sid (from GitLab), Sid goes through a lot of their learnings, very elucidating.