An error message appearing directly after page load on banner pages [i] displays in a jQuery UI window [ii]. It should use mw.notify [iii] [iv] instead, because the current presentation of the error message is rather uncommon (making the Wikimedia platform less uniform) and annoying (it sits at the center of the screen, without standing out enough for the user to easily identify it, but covering enough content to make reading impossible without closing it). Also, jQuery UI is being deprecated, so code should be moved away from it, and in this case it can be done without losing any functionality, and otherwise considerably improving the UX. mw.notify’s second parameter can also contain a type property that can make the message stand out even more, although the default info type already stands out a lot more than the jQuery UI version.

[i] E.g. https://meta.wikimedia.org/wiki/Special:CentralNoticeBanners/edit/wle_2022_ke
[ii]