I don't like using propprietary software, not a lot of the geeks in the IT sphere do considering a lot of them develop software and open source is great for faster bug fixes amongst other things.
Starting note: Whenver I refer to Linux in this article, I am referring to the Linux kernel. For the purposes of the GNU folk, in this scope of this article, they are equivalent.
Many pieces of software, open source or otherwise, uses something like Sentry. The problem with things like Sentry is that they may collect data about users unknowingly, Windows telemetry has been forced to be on in Windows 10 and soon 11, and macOS checks if Apple has authorised every app on your system via Gatekeeper.
Proprietary software may have useful parts of its documentation hidden to only licensed developers or to the internal team at their company. This means that potentially performance enhacing tricks can be hidden to the developer of the software which may allow for unfair competition.
You may be able to delay an update here and there to stop all your things changing but every new version of Windows moves the place of literally everything which makes it harder for disabled people or elderly people to interface with the program when they're used to older versions, while with open-source software you can roll back the changes or create a new fork.
The Windows NT kernel has been around for a bit longer than Linux but in total Windows NT (the kernel technology behind the Windows OS) has about 194 vulnerabilities with a CVSS score over 4, meanwhile the Linux kernel has about 2,000 vulneraabilities with a CVSS score over 4. Now you may think "Oh, no Linux is more vulnerable than Windows", however keep in mind vulnerabilites reported by security reporters and CVE are probably fixed. Windows has a history of having the NSA hide exploits for years before reporting them so that the NSA can use them for "national security" (read: spying on its citizens) meanwhlie the higher number of CVEs in Linux shows that more people can find bugs and fix them in the kernel. Why you may ask? Because its code is open and everyone can see the problems and fix them quickly! This allows for fast patches to be delivered and for bugs to be fixed before someone can exploit them!
So this is why I personally think proprietary software is bad! Use open source and be happy!