On the contrary, I think open source strengthens everything. Where copyleft leaves users of other people's software looking over their shoulder to confirm they haven't broken the license, with open source licenses I can release some work and not worry about how it's used, and I can use somebody's work without fear that they will come after me later.
It does strengthen proprietary software. It also strengthens everyone else's software. It's the rising tide that floats all boats.
What you're referring to is actually permissive licensing (or as I like to call it... /s). It's a scam.
It works fine for trivial pieces of code that no one cares about. But for bigger pieces of software, you're donating your time to Amazon, Microsoft and Palantir. You're volunteering for them. Why would you do that? If they want you to work for them they should pay you. If not for your wallet's sake then for the sake of hurting bad companies.
Copyleft is easy to comply with. Being scared of copyleft is like being scared of servers (which most programmers are according to DHH!).
It does strengthen proprietary software. It also strengthens everyone else's software. It's the rising tide that floats all boats.