Take to Apple - they will replace IF you fall under 3 year (possibly 4 year window as I believe it was extended.)
Failing step 1. You can try / (go all in) with Listerine mouth wash - clear version is preferable. I've had some success today (not entirely successful but 87% better), still a bit more to go.
This will remove some/most/possibly? all the reflecting coating from screen. Just power down mac.
Apply a tiny dab of clear Listerine to a baby clothe and rub rigorously.
Using a household clothe could result in scratches to screen.
Invest in the softest baby cloth money can buy / or use the iPhone screen wipe you get with iPhone /iPad. You need to press hard / really hard / but not so hard that you damage the LCD crystals. It was the first time in my life where the whole wax on / wax off meant anything as the screen lamination is kind of waxy. rubbing back and forth. You need to dry it / wet it for it lamination to budge. For some users - it maybe too soon in the deterioration process. Be patient it's likely to take a few sessions.
WARNING - DO NOT TIP the bottle of liquid onto screen like this guy.
N.B. You could try a polishing (an extremely soft / gentle) pad attachments on power drill if baby clothe isn't working. (this could easily wreck your computer. DO NOT have mac powered on.)
I still have some reflective coating 8% left on screen that won't budge.