By golly. I think I've got it.
Someone (or many someones) at Esri has a special forces or motorsport background!
They firmly believe in the mantra "Slow is smooth, and smooth is fast".
Unfortunately for them slow software is just slow software.....
I've just spent 3 days (billable total) on a complex map series in Pro.
The data is quite simple (low object count), only a few labels, small area, single imagery basemap with 2 overlaid raster images, etc. Think your typical NI43-101 or JORC resource report series.
There is no excuse for the GUI delays in 'mature' software. In many cases the data process, map update / render process will be complete and I have to wait for the ribbon to work out what it wants to do next. The number of dead clicks I made due to clicking before the GUI is ready has killed my hand and raised frustration levels to a record for this year.
Something as simple as pasting a layer from another map, moving it to the right order and then removing another layer is an exercise is patience. The same actions, with the same data, in ArcMap is much more responsive.
No other application I run has this level of blatant disregard for efficiency.
For those playing along at home Pro is running on a 5950X, 6900XT, 64GB and storage is a ZFS array accessed via 10GBE.
Most data processing actions are pretty decent these days bar a few i.e. still a case of pick your fights and use ArcMap/Catalog/QGIS appropriately, but general simple tasks should not cause a full GUI redraw and disregard all input during that time.
I did lodge a case against this a while ago and after some time the response from Esri Inc was "work slower". There you have it folks.
P.S. I do believe in the slow = fast philosophy. Try it. Turn down your mouse acceleration a tad, and look at moving your toolbars around so you have to move the mouse/your hand less. You will have more precision and the mouse won't replicate your heartbeat when going between targets. You are more likely to click on the right item first time as well. In ArcMap you can then get into a rhythm of enter, click, type, tab, type, move, click, enter, arrow, enter,......repeat, etc.
Not in Pro. In many dialogs you still have to click in to type (e.g. setting field length in new field form), or the delays and random pauses makes the application fall behind, requiring you to slow down and wait a random period between each task.
O shoot - I forgot. You can't optimise the toolbar layout in Pro....... Unless you count customising the poor Quick Access Toolbar to an inch of its life with all the tools you use everyday.
ArcGIS Pro turned 8 a few weeks ago.