I've never seen a scenario like this and even with the ideal case of current abstraction frameworks there is always tedious grunt work that juniors get to cut t

I've never seen a scenario like this and even with the ideal case of current abstraction frameworks there is always tedious grunt work that juniors get to cut their teeth on - doing minor adjustments to fine-tune requirements, adding minor functionality, etc. Stuff where you don't want to waste time and focus of senior devs. The only scenarios I saw where juniors were not needed is overly complex systems where the barrier to entry was so high you needed a huge amount of upfront knowledge to do anything. Those were not good projects to work on.