Windows XP
When Windows XP first released, people criticized it for having a theme that they hadn’t seen before in Windows. People thought it was very kiddish and appealing to children, not being taken as seriously for the large userbase of the time. There were also criticisms about how fragile Internet Explorer was (I’m not kidding, I was there and Internet Explorer back then was at its most insufferable.).
But these days, just because of how bad Windows 8, 8.1, 10 and now 11 have been, people have praised Windows XP so much.
I actually asked my dad (and he did) to take me to the Windows XP Tablet PC Edition launch event in LA for my 14th birthday.
I got one of those when I was in college and it was perfect for that. A little underpowered but great for writing, notes, etc.