Understand the frustration. I’m currently writing a proprietary software service/system that is largely based on FOSS software. I expect to sell it for real $$. One must just stay away from areas that are easily commoditized. Sure there’s a risk that a FOSS solution might emerge in your space - but risk from a low cost producer has always been there. I personally do not view FOSS as a barrier to commercial success.
depending on the licensing, you might lose any / all profits by having open source within your product
if you are servicing a niche, the likelihood of an open source solution popping up is very low. general systems with mass appeal is usually the target of open source