For small companies things like vercel, supabase, firebase, ... wipe the floor with Amazon RDS.

For medium sized companies you need "devops engineers". And in all honesty, more than you'd need sysadmins for the same deployment.

For large companies, they split up AWS responsibilities into entire departments of teams (for example, all clouds have math auth so damn difficult most large companies have -not 1- but multiple departments just dealing with authorization, before you so much as start your first app)