I recently upgraded KDE. Back before an update the feature to close a window old-school windows 3.1 style, by double clicking the title bar menu worked great.

Now, when I select the option to enable the feature it says
"Click and hold on the menu button to show the menu".

Not great, how can I get the old way back?
Why did the devs make that change? Can they be asked to revert? Or add a click and hold option?
What version of kwin do I need to run to get regular single click show menu and double click closes functionality?

A video of what you are doing would be very enlightening.

Upgrade from what to what? Exact Plasma version, distribution? Don't blame the devs without knowing it was not the distribution, and read the change-logs of the versions (https://kde.org/announcements/), design changes and decisions are always explained (if that really was the case...)

Single and double click can be configured in the Desktop settings, check your system settings Workspace section (Window Management in the Workspace section to be precise)