Out of any software tools I use frequently, Unity is the one that brings me the most joy.
Any reasonably complex interface is essentially a game whether it's a music composition app, simulator, MMO or even a basic form.
The basic abstractions of entities and components sometimes feel like they could apply to any software project. It's seamless to animate something, add physics, style in ways that would seem mind boggling in other environments I've worked in like Python or Javascript.
You can learn so much going over basic Unity tutorials on Youtube and disassembling Unity games on Steam.
The asset store has many people aggressively experimenting with better user experiences for doing certain tasks whether its character skinning or node based programming, many of the best assets end up added to Unity by default.
Unity is not mostly used for mobile games, some insanely complex games are made in Unity. You can check out this list on Steam https://store.steampowered.com/curator/31285130-Unity-Engine...
Unity ML agents is the single most exciting ML project out today which helps you create the most complex Reinforcement Learning environments you can dream of.
Unity ate the indie game market but I think they will also eat Robotic simulations, Animation, interior design, VR, Web apps and Desktop apps.
Can't wait to buy shares.