By my lengthy experience all those automation developers have to do some testing too.
The best time to fully automate checks and actions for running on a CI Server ist AFTER the current development cycle. When most bugs are found and fixed.
When you develop a full automation during the current cycle you always stumble over bugs. Some are hindrances which need to be removed aka fixed. Some don’t bother you much, but you investigate and report some anyway.
This is all this “manual” work.
A testers work, the same as you do.
I doubt there are not many people which doing pure automation in testing, by their actions.
Finally automation is just a tool for testers. Not a replacement.
(The next rant would be about that automation is only one way to use development in testing)