Are you familiar with the recent Mercedes-Benz Source Code Exposure [1]? It's a good example of why you should consider a secrets manager for any serious project. Environment variables come with a lot of risks and are difficult to manage as teams grow. 1) ENV files are easy to accidentally push to a repo. 2) It's easy for environment variables to get out of sync among developers. 3) In the case of exposure, it's often difficult to rotate secrets quickly. A secrets manager removes this risk - but you do need to trust whatever service you decide to use, as well as make sure it's compatible with your infrastructure/cloud environment.

[1] https://www.doppler.com/blog/lessons-from-mercedes-benz-sour...)