Is automating away all the boring stuff actually the highest net business value approach you can take?
It might be necessary to let people do it to retain senior people and keep their morale up, and I've certainly seen companies be successful by letting good people overengineer things simply because it lets them attract good people and have them around when they're needed, so if that's your strategy, go for it. But you might be better off having a person with market salary $X spend a week doing something they don't yet find boring (and will learn from so that they can become senior) than having a person with market salary $2X spend three days automating and writing tests for their automation.
And there are a lot of interesting real-world problems (as in would-produce-business-value problems) that can't be automated, like gracefully remediating a legacy system where each user was able to get their own weird requirements supported. In the process of getting all the users onto a system you can automate, you need actual human time to work with each user and understand what they need out of your API surface, and while having senior people available is necessary for the complicated cases, it's unlikely to be necessary for all of them (and again, the ones that senior folks would find boring are good opportunities for junior folks to gain experience).
You seem to have two arguments here: training people up and short-term economics. The former is irrelevant to your point. Yes, if you have junior people, it's good to find things for them to do that are at their skill level. But that doesn't mean that there's no high-skill way to do the same work.
I don't think the short-term economic perspective really means much in the long term. Sure, if you spend $6x automating something a junior person can do for $5x, then your apparent extra cost is $x. But that's only true if a) the problem never comes up again, and b) no problem particularly like that one comes up again. Given the history of our field, that sounds like a poor bet to me.
It might be necessary to let people do it to retain senior people and keep their morale up, and I've certainly seen companies be successful by letting good people overengineer things simply because it lets them attract good people and have them around when they're needed, so if that's your strategy, go for it. But you might be better off having a person with market salary $X spend a week doing something they don't yet find boring (and will learn from so that they can become senior) than having a person with market salary $2X spend three days automating and writing tests for their automation.
And there are a lot of interesting real-world problems (as in would-produce-business-value problems) that can't be automated, like gracefully remediating a legacy system where each user was able to get their own weird requirements supported. In the process of getting all the users onto a system you can automate, you need actual human time to work with each user and understand what they need out of your API surface, and while having senior people available is necessary for the complicated cases, it's unlikely to be necessary for all of them (and again, the ones that senior folks would find boring are good opportunities for junior folks to gain experience).