Cleaning help needed -- glass shower door

My mother is a hoarder. I recent,y did her bathroom and I was completely shocked that the glass looked like new

I used a spray mr muscle cleaner that made a loud fizz noise, left it for 15 minutes, then I used a brush meant for dishes one that has washing up liquid on the handles I scrubbed with that, then with a wet towel and a lot of work, I rubbed it clean, then I dried it with a towel til the smear was gone, It was a horrible job but the glass came up like brand new and they were pretty gross

Personally I think it was the dishwashing brush

I have used - KRUD KUTTER KK32 Original Concentrated Cleaner/Degreaser, 32-Ounce link

I have been very happy with NORWEX DESCALER, you may have to use it 2X.... I would also use a scrubber/scraper made for a glass topped stove. GOOD LUCK, I HATE cleaning shower doors

We use CLR on ours and it works really well   

Try toothpaste if all else fails. It works

Could they be frosted to begin with?

Have you tried cleaning the doors with a powdered water softener like Calgon? Years ago I had success with mixing Calgon water softener (powdered) and a powdered cleanser like Comet to clean a build up of soap scum from shower doors. You could try starting with just the softener and see if that helps to dissolve the build up. I've also read that Borax will work as well.

I had the same issue, although mine hadn't been on as long. The only thing I found that worked was Glass/Ceramic stove top cleaner, the cream type. I'd tried pretty much everything listed on here, most notably CLR, Magic Eraser, Drill brush, dawn/vinegar, and Kaboom. I thought I was dealing with soap scum. Nope. Hard water spots. The glass stove top cleaner was like magic.

If it has been 2 years, it's possible the hard water minerals have pitted the glass and there is nothing that can be done. But try out that cream cleaner. I literally shed a tear because I'd been so frustrated over it and it worked so easily.

Edit: if it does work, then the way to keep it from building back up is to use a squeegee on the glass daily. The water sitting there is what etches it. And clean regularly. Frequency is more important than product once you're starting from a clean surface, in my experience.

Our kettle gets snowy from the mineral. Cold vinegar does nothing but hot vinegar gets it off just like that. I poured the hot vinegar into the Keurig reservoir and it bubbled and carried on and all of the hard mineral came off.

Steam cleaner with a brass brush on the nozzle. Best thing I've found so far. Bonus is no cleaners needed.

This!

CL R works on mine. I have to spray it on thick and let it sit.