The problem is more so maintenance.
The expectation of FOSS is that the users and maintainer work together to resolve bug fixes/features/security issues.
However many companies will dump these issues to the maintainer and take it for granted when they are resolved.
It's not a sustainable model, and will lead to burnout/unmaintained libraries.
If the companies don't have the engineering resources/specialization to complete bug fixes/features, they should sponsor the maintainers.
A company finding a bug and opening an issue on an open source project _is_ contributing.
What happens next is completely irrelevant. The maintainer can 100% decide to just ignore the issue or close it.
Opening issues doesn't create unmaintained software. In fact it helps.
No the expectation of FOSS is that code is provided AS-IS with NO WARRANTY because that’s what it says in the license.
It’s OK to say “No” or “Pay me and I’ll do it right now” to companies doing this.