resolution - since 2019 update illustrator's menus, tools and swatches are too big?
It seems like it can't tell its on a 5k monitor?
See comparison below.
Illustrator 2019 compared to indesign 2019
Starting CC 2019 we are scaling the user interface a little on high resolution devices. To turn that off please use the small value as described on this page to get back the behaviour of previous release.