Hypercard was absolutely dope as an entry-level programming environment.
Even modern desktop Linux pales in comparison because although it’s technically possible to change anything imaginable about it, to do a lot of things that extensions did you’re looking at at minimum writing your own DE/compositor/etc and at worst needing to tweak a whole stack of layers or wade through kernel code. Not really general user accessible.
Because extensions were capable of changing anything imaginable and often did so with tiny-niche tweaks and all targeted the same system, any moderately technically capable person could stack extensions (or conversely, disable system-provided ones which implemented a lot of stock functionality) and have a hyper-personalized system without ever writing a line of code or opening a terminal. It was beautiful, even if it was unstable.
Computers have been “fast enough” for a very long time now. I recently retired a Mac not because it was too slow but because the OS is no longer getting security patches. While their CPUs haven’t gotten twice as fast for single-threaded code every couple years, cores have become more numerous and extracting performance requires writing code that distributes functionality well across increasingly larger core pools.
Mainframes are also like that - while a PDP-11 would be interrupted every time a user at a terminal pressed a key, IBM systems offloaded that to the terminals, that kept one or more screens in memory, and sent the data to another computer, a terminal controller, that would, then, and only then, disturb the all important mainframe with the mundane needs or its users.
What killed that balance wasn't raw speed, it was cheap RAM. Once you could throw gigabytes at a problem, the incentive to write tight code disappeared. Electron exists because memory is effectively free. An alternate timeline where CPUs got efficient but RAM stayed expensive would be fascinating — you'd probably see something like Plan 9's philosophy win out, with tiny focused processes communicating over clean interfaces instead of monolithic apps loading entire browser engines to show a chat window.
The irony is that embedded and mobile development partially lives in that world. The best iOS and Android apps feel exactly like your description — refined, responsive, deliberate. The constraint forces good design.