This is what everyone’s approach should be. The product itself should be standing on the shoulders of FOSS giants. Everything else is just quality-of-life improvements and tools which should be paid for if they speed up your productivity or decrease your mental load.

Proprietary software lock-in in your product can generally be very damaging when things go wrong. I know of one company which was so throughly fucked over that they had to halt all feature development for 6 months while they were busy building a replacement. Cost them enough time and customers to a competitor. For non-product stuff, replacing proprietary software is a bitch but far less disrupting.