This is a common thing I hear but it's not true. The hamburger menus were done to save space and reduce clutter, not out of any desire to be a tablet app. I sympathize with your criticism but it wasn't done for that purpose, it's just a coincidence. Also I should note, there are many non-tablet laptops that happen to have touch screens. These are not exactly rare these days, and AFAIK that was also a hardware segment that Microsoft was targeting, not just tablets. They weren't just making touch interfaces to sell the odd Surface or two. Sadly I don't know of any more elegant solution to this than what they're already doing, apps that want to work well here always have to straddle an awkward line where they have to support both traditional mouse and keyboard operation, as well as touch screens, at the same time. It's not an easy thing to design apps for.
To actually make good native touch/tablet apps in GNOME, you need to use a separate library called libhandy (renamed libadwaita for GTK4), and the app needs to be designed in a different way. You can usually tell the difference with an app made specifically for touch screens because it will totally de-emphasize the keyboard and mouse. I see more and more of these type of apps but only in the last couple of years, and it's mostly not to target tablets but to target the new open source phones e.g. Librem, Pinephone, etc.
>The hamburger menus were done to save space and reduce clutter, not out of any desire to be a tablet app.
"Save space"? That's a laugh. Reducing clutter is ill defined and probably subjective, but saving space? Saving it for what? The default window decorations, widgets, etc are bloated, not slim and compact (as they would be, if they were saving space.) Everything has huge margins, big buttons, and empty voids. "Saving space" is not a principle Gnome cares about.
Do you know what huge margins and big buttons are actually good for? Touchscreen interfaces designed for fat fingering. That's what Gnome cares about.
Again, what you are saying is not correct. You may be comparing their designs to other apps developed for other desktops using other toolkits, but that's not what is influencing GNOME. The space is saved compared to previous designs that were used by GNOME. Please consider comparing an old style GTK app with a new style GTK app:
The old style has four bars at the top (titlebar, menubar, toolbar, secondary toolbar). The new style merges them all into one bar and moves the menus into the hamburger menu. The margins may be bigger in the new style but ultimately, space is saved and the UI chrome is reduced. Also, GNOME Builder is not an application designed totally around touch screens -- it's a text editor, for typing into.
I sympathize if you don't like this style of app (and I encourage you to use different apps if you were used to having a lot of menus and toolbars, and you don't like the new style of GNOME apps), but what you are saying about the design goals and motivations does not match what the developers are actually doing.
To actually make good native touch/tablet apps in GNOME, you need to use a separate library called libhandy (renamed libadwaita for GTK4), and the app needs to be designed in a different way. You can usually tell the difference with an app made specifically for touch screens because it will totally de-emphasize the keyboard and mouse. I see more and more of these type of apps but only in the last couple of years, and it's mostly not to target tablets but to target the new open source phones e.g. Librem, Pinephone, etc.