And MacOS is even worse. I just bought my daughter a MacBook and sat down with a Mac for the first time since 86. My expectations were high. I thought I was going to see a Unix GUI done right. Instead it’s nearly as clunky as CDE.
MS may deserve grief about some things, but dang, Windows is about as polished as a product can get.
No, it doesn't.
Explorer is the file manager application on Windows. The file manager application on Gnome is called Nautilus, and Nautilus has had thumbnail support for a very long time.
This is about the file picker dialog, which both on Windows and on Gnome/GTK+ is not coming from the file manager. You can say that dialog should have had for thumbnail support for longer, sure. It's also correct that Windows added thumbnail support to its file picker dialogs earlier. But Win98 did not have this, either, and Windows at least for some time did not have parity between the file manager and the file picker dialog.
It's surprisingly common for DEs across different operating systems to have several independent implementations of file lists/icon views between the file manager, the desktop background and the file picker dialogs. I think across Win, Mac, Gnome, KDE this actually describes most of these systems for most of their history.
You sometimes do find code reuse or even sharing a process between the file manager and the desktop background. Windows has done this, and Gnome also had a phase like this.
KDE recently unified the view code for the file manager (Dolphin) and the file dialogs, but the desktop background has distinct UI code (with the same directory model backend, and shared code for thumbnailing, context menus and other bits). In that case the reason is different UI frameworks (Qt widgets vs. QML).
Windows still delegates to legacy Vista(XP?)-era UIs for certain settings.
They've stopped supporting the Windows 1.0 feature of clicking the window icon for the window menu though (and broke the "double click the top left icon to close" workflow in their weird new app designs, sadly).