I believe if you are fortunate to have Metal working Light mode works fine. There is some transparency but other than that it looks ok (see screenshot #1 and #3). Exceptions: the light menu bar because of its transparency starts to look bad, in my opinion, is when you use a dark background (see screenshot #2).
This is on a Mac Pro 3,1 with Metal. I will check my 2012 Mac mini and see if it behaves the same. If so this more on Apple than anything else. The Menu bar on light not doesn't need to have transparency and I think several users on her have provided a workaround for this.
Now where this all gets worse if if you don't have a new display. My Dell DVI-D is much more dimmer than my new ASUS. And you are gonna suffer more there with light mode than with dark mode enabled.
Also the menu bar on dark mode works because it has much less transparency applied to it.
If light mode and that important and things like reduce transparency or other workarounds don't work, then you could stay on High Sierra longer. Apple has literally minified Mojave's features. It seemed to way more pronounced with the screenshot tools in the first beta to where the GM is now. It either that or I hardly notice what features we are getting beside dark mode. lol. I do like dark mode though and that is my biggest reason besides staying current to use it.
A graphical alternative to getting light mode to work:
By the way since the menu bar shows the background you could make a background image that has a white layer on top of the background image. This would be another workaround for light mode and it would not require swapping frameworks or kexts. I could make a photoshop action that does this or possibly make a webpage in javascript that could do this as well. This would just kill dynamic backgrounds unless there is a way to make these with the menu bar area fixed in the dynamic background.
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