The only exception I have to this is S3. There are so many S3 compatible providers that I don't see any problem with using S3. There's even MinIO for self hosting and local development!
Some more suggestions for open source components:
Redis for caching and queueing
SMTP for mail
Nginx for load balancing
Cron for scheduling
Some more suggestions for open source components:
Redis for caching and queueing SMTP for mail Nginx for load balancing Cron for scheduling