Except I don’t think it’s a “simple overlay”, it’s a Critical Power Curve.
Should they get it right - YES
Are there things I’d rather they put their finite resources into first - YES
In the grand scheme of what you are paying for with Zwift this isn’t even small fry, BUT it also looks very bad as it’s the display layer, the menu/ 1st exit panel with the HR & disappearing Power histogram is also a bad look.
Are there good external solutions out there - YES, for those who want to use them and possibly pay for them too.
I use Golden Cheetah because I used it before I got on Zwift.
There are lots of bugs Zwift need to fix, I’m hoping like all good IT based Companies/ Depts that they have prioritised them and are hitting with the bug hammer, they do need to sort out the UX/UI as it is customer facing, it’s the shop window and that is easy to forget when you’re up to your neck in re-working serverside code to fix a deep lying fundimental issue.
Some people just don’t remember the “fun” of indoor training before Zwift, it were proper mingin’ r kid.