You definitely have some good points, but I think there are good responses. (1) It doesn't have to be perfect to be better. (2) You don't need everyone to read

You definitely have some good points, but I think there are good responses. (1) It doesn't have to be perfect to be better. (2) You don't need everyone to read the source code, just a few people. (3) Open-source not only makes it technically harder to do malicious things to users. It also (hopefully) improves the incentives.