Fx. LAMP and MEAN stacks are very manageable.
With hosted container services they are also very easy to set up.
Even in a high volume environment, you can cheat with caching services like Cloudflare or Akamai. Making even that manageable to learn for a single person.
So i would say he is wrong.
Granted it does take a lot of time to learn all the tools.
Depends on the stack.
No-one forces you to build a rocket-ship-stack.
Fx. LAMP and MEAN stacks are very manageable.
With hosted container services they are also very easy to set up.
Even in a high volume environment, you can cheat with caching services like Cloudflare or Akamai. Making even that manageable to learn for a single person.
So i would say he is wrong.
Granted it does take a lot of time to learn all the tools.
Sounds reasonable. You own your own stack. So you become a full stack in your own right.