Detailed response. Lemme touch on a few.

Open source software are vulnerable to stack-smashing attacks. They are known to be less reliable, that is why critical industries like aviation and medicine mostly use proprietary.

Open-source backed by big tech companies are different because they do not suffer from a lot of the things I mentioned. These teams are usually assembled from the start, they have meetings or work at a specific place, they are well funded so they do not just quit the project, there is a lot of gat keeping and not just any joe-blo can "contribute", they are industry standard professionals that know what they are doing. In this case the only downsides to open source backed by big companies are criminals stealing the source-code and re-selling the software as theirs and the company not being able to monetise it as they would do a proprietary software.

Regular open-source software that are run by under-funded, under-trained, non-screened, "coders" are just pure garbage, unfortunately, that makes up over 95% of projects on github. They are just unfinished, low-effort, low-quality software. Go on github and see for yourself.