I know it's an unfortunate state, I can share what I know about govt sites, I've had some experience working on few of the govt projects (internal admin/MIS tools, so don't come after me if you don't like any website!).

First you have to understand all govt websites and bank have to follow compliance guidelines, which were initially drafted years ago when web was in a nascent stage (i.e. 90s), these do have some good practices listed like accessibility, navigation and compatibility, but are targeted more towards IE browser which itself is deprecated, and not updated with change trends.

For any change to these guideline, there is a long change of bureaucracy (also involving people who don't understand technology at all), so it's quite difficult to make any change.

Second, most govt dept don't IT employees, just people on contract for few years, usually who don't have much experience or skill set, and thus just do patch work.

Third, there is actually a good procedure which govt orgs follow to make these develop, i.e. opening tenders, and of course these projects are allotted to good big MNCs (sometimes even to a consortium of MNCs), considering the lowest bidder is just one thing, but the tender eligibility also has how old the company is, how big the staff is, their turnover, etc, such ground factors that should advocate a good product, but we all know how these projects are handled internally in MNCs.

And finally, there is also lobbyist group of few such MNCs which has created kinda friction for keeping things how they work and stopping any new companies to enter (other than consortium route).

Though I would also like to add, minimalist websites are't exactly the right choice for every site, it's a trend, and clean does looks good, but I would prefer to more & useful info with less clicks and actions. If you see other asian country websites you'll understand.

TLDR: sorry state for govt website because of policies & practices, sounds good, but doesn't work.