Sadly, the internet as a whole seems to disagree. Even the most useful resource on the web one could use over plain HTTP, Wikipedia, only allows connections over HTTPS. I guess it kind of made sense as part of the campaign to push the internet as a whole over to HTTPS, but anyone who's connecting to any website over normal HTTP these days is doing so because they literally can't use HTTPS.
If you are concerned about accidental login or API keys without TLS, then you can consider supporting mutual TLS, which improves security (and flexibility) in other ways as well. (You do not necessarily, have to require mutual TLS, in case someone prefers to use a username/password login, or 2FA or something else like that instead.) (In the case of login forms, you can have the links to the login forms to always use HTTPS, in order to avoid the problem.)
You'd think the person was creative but maybe insane.
This is the exact same feeling I get when I see web "apps".
TLS 1.2, the standard, may be from 2008 but support for it in browsers did not start to appear until around 2013.