Nice screenshot however that raises a couple questions like what year are you in, what mode are you playing on, map size, difficulty, mods, etc...
Approximately 2450, Ironman, 1k stars, 5x habitable, admiral, mods - except graphical,
Automatic Pop Migration.
As for your point, yes Stellaris has no way to afk at the keyboard which is fine by me.
K, at a certain game speed, each important object generates some events from time to time. Some of them can be truncated to series of related events (for example, new pop + queuing of a new building or a district + completion of the latter + optionally, resettlement). As game goes further, empire goes wider, so total count of sources of such events goes higher.
Let's say, you could meaningfully handle %insert_desired_number_here% of such events per minute in real time (w/o pausing), IF user interface isn't already laggy due to lategame.
Obviously, from certain point, count of events happening per minute exceeds your ability to handle 'em, so you can't handle your empire anymore. It become too big to handle via manual management. Meaning, you need some manageable automation for common-and-routine-and-everywhere-happening events. Otherwise, there is a hardcap of expansion exists.
upd
And it's very funny: due to overall game mechanics, and, especially, crime, gestalts, that must be better suited to wide playstyle, hits hardcap of expansion earlier than non-gestalts, because gestalts requires way more micro.
/upd
mod train mode: on
for example an auto-resettle button would be pretty friggin great for me.
Well, I've linked the mod I using for this

mod train mode: off
Before the economy patch I literally alt+tabbed on fastest for long periods of time because there was simply nothing to do whatsoever and I do not want that to happen again.
The thing is, Stellaris is mostly a routine-in-another-routine game, most of the time you don't need to make decisions, except the beginning, when you still looking for the optimal way to handle common events. After you have found the way, you will wish to automate it, in order to be able to make something bigger.