That is very helpful and an excellent account of your position.
I suppose the definition of “best” is crucial, here, and there will be many different interpretations of it. For myself, there are two really important elements: the look, feel and operation of the UI; and a speed-bump-free workflow. Obviously there are other important elements, not least of which is the capability and functionality.
Open source is not important to me, per se, although I obviously appreciate not having to pay a licence fee. But there is no “matter of principle” thing for me, as there obviously is for many people.
Cross-platform is also not important to me, as I always use Windows (I run Linux Mint in a virtual machine, but prefer Windows). In fact, I think cross-platform can be a problem because such programs hardly ever adopt the look, feel and design language of the OS they are running on. Most cross-platform programs look like orphans that don’t belong anywhere, using generic visual elements that look slightly “foreign” to whatever OS you are using.
The other disadvantage of open source is that the applications rarely get as much developer time as the commercial products, so they lag behind when it comes to functionality and keeping up with the operating system design languages. Libre Office is an example - to my eyes it looks ugly and clunky (like it was written for Windows 95 or earlier - oh look, it was), and misses out on some really basic functionality (text selection, for example, is a bit rubbish). Compare its look with Softmaker Office (a proprietary offering in the same space), which is so much cleaner and more modern. Another example: take a look at the Affinity suite from Serif and compare it with any open source graphics editor (or vector or DTP application). It started as a clean sheet design, launched in 2015 after six years of development effort. It’s outstanding, and makes GIMP look amateurish.
So, it turns out we disagree on cross-platform and open source! Having said that, I think KiCAD does well on the UI front. Yes, the menus, toolbars and dialogs look like Windows 98 or thereabouts, but it is learnable, internally consistent and the consistency between different platform versions is excellent.