It probably is, and that is just fine. As long as enough of us value being able to use Ruby they'll do ok. Not everything needs to aim to become a unicorn.
I can only speak for Unity until versions till maybe 2019 - and I never developed a full commercial title with it - just a few game jam games - so maybe I'm not the best authority on that... But I think it's quite far away in many of those features
Sure you can try out your game immediately in the editor, by pressing the play button - but can you edit Source code and it will be immediately applied without restarting and without losing the current game state?
You can edit and adjust scene objects in the inspector during play mode but those changes are usually thrown away after quitting play mode.
I never did serious mobile dev with unity but I same as above... updating and editing your game source persistently at runtime during playing doesn't seem possible, since it's completely compiling everything into an Android package right?
Building for all desktop platforms under a minute - this is 100% not true..... Almost all of the last hours of game jams where I used unity where spent in worry waiting for a long build process not being sure everything works all right afterwards - and that was always for just _one_ platform at a time...... DragonRuby builds your games into fully functional Windows, Mac, Linux, HTML5 and FWIW Raspberry Pi builds in under a minute in total for all those platforms. I don't know of any other Engine (except maybe LÖVE2D which is interpreted in its basic nature and doesn't need building) which can do anything close to that speed
Persistent flexibly modifiable game state? - maybe there's something in the asset store - but out of the box?
Cross-platform File storage is the only thing where I can see that that is probably a well solved problem in Unity....
I cannot speak for the other game engines. But in general it would be nice if you back up your claims.....
Am in the midst of shipping a medium sized game in Unity and I can confirm your takes are correct/relevant today. Unity is incredibly frustrating to me, and I would really aggressively challenge the notion that Unity is aimed at any sort of "Developer Productivity". More than anything it's a dumpster of features to allow Developers, Artist and totally nontechnical/non IC contributors to all contribute okay-enough. But the features that go into making Artists productive are at times orthogonal to those that make Devs productive. It's all a big tradeoff.
Godot is smaller and has way way less learning material (and no Asset Store), but purely from an Editor perspective it's miles ahead from a dX perspective.
Playing from editor is the testing on desktop. You can make a parallel builds in Unity with the new build tools. Hot swapping code breaks down quickly as complexity increases (it’s also supported by default in Unity). With nested prefabs changes can be made while scenes are running and preserved. You can debug an unity game remotely with Rider or Visual Studio, you can add new code, change execution order, memory, etc. I guess Ya got Unity best on build speed though; although, I bet a lot of what you saw as build time was asset conversion. In my experience with unity I rarely leave the editor/rider combo and I only make builds when testing new libraries (because of IL2CPP) and for performance analysis. It is much, much faster to iterate through the editor than hot swap could ever hope to achieve; I can test every resolution, notch configuration, etc without leaving the editor. I have built professional games with custom engines, unreal 3, unity, and torque and Unity is by far the most enjoyable to make games in.
It probably is, and that is just fine. As long as enough of us value being able to use Ruby they'll do ok. Not everything needs to aim to become a unicorn.