What is your monitor size?
(Edit)
You see the app's font size is on par with the text size of your KDE panel. If gnome increased it, it would look totally out of place.
Also centering content is a valid design choice. Many websites do that on large/wide monitors. It improves readability. An example might be the design of pi-hole's UI.
If readability is your issue on gnome on wide screen monitors you should also have issue on reading the time and date on the KDE panel as well.
In other news, earth is deemed as the most hostile environment for any living organisms.