I do and have done both and a blend. Secrets for external services needed in dev usually in parameter store. Kinda depends on the existing work flow. There is so much to do you should be tackling problems that move the needle and chip away at small stuff, pet peeve stuff in smaller time-boxed increments.
So with .env file:
- developer adds to .env
- pushes code
- all developers see failures in dev env due to missing env var
- all developers search slack/email to figure out what went wrong
- all developers update their .env file and things are working again
————- In gp’s comment ———-
- one person works on feature that introduces new config
- failure happens in their local environment
- they update config backend and push code
- all other developers get updates with no changes needed