I am not sure how the open source vs. closed source plays any role in this. You can support a feature with a closed source app as much as you can with an open s

I am not sure how the open source vs. closed source plays any role in this. You can support a feature with a closed source app as much as you can with an open source. TLS implementations having serious problems as the last few years proved it. We need a more fundamental change in security protocols and implementations, using reliable crypto (for example elliptic curve cryptography) and implementing them in safer languages (like Rust).