Basically, "KiCad is just as good as Altium" is a typical open-source software fanboy claim. It's just as untrue as the claims that "LibreOffice is just as good as Microsoft Office" or "GIMP is just as good as Photoshop". In every case, the open-source program can do all of the basics (and then some), but simply cannot compete with the feature sets that those established commercial programs built up over the course of decades.
While I have every reason to believe that open-source server software (servers, databases, etc.) can do everything their commercial counterparts can, that simply isn't the case for desktop software. The fact that no open source desktop app has ever managed to dethrone its commercial counterparts... well that speaks volumes -- s does the fact that in many cases, open source server software has dethroned commercial equivalents. That means the market is willing to go open source when it's good enough. And the corollary that open source desktop software just isn't there. (Nor do I think it ever will on the whole, for various reasons, but that's well beyond the scope of this discussion.)
Maybe off-topic since I don't know about Altium/Kicad, but I have to disagree. I don't really like LibreOffice, but I don't think MSOffice is any better. It was funny when the .docx became a thing and suddenly MSOffice users with older versions couldn't open .docx documents. I know many people that changed to LibreOffice just for that. Of course, these were individuals. Bureaucrats and people in any companies just asked their bosses to upgrade.
About Gimp/Photoshop, there's one thing Gimp never will do: to handle Pantone colors, because it's propietary. However if you work in pre-printing, you need to handle Pantone. Just imagine what will happen if say a big bank purchases a full page in your paper, then there's a disagreement about the color used in their corporate logo. Unless you can show evidence you used the correct Pantone reference, you are screwed big time. So, no, GIMP never will replace Photoshop in these habitats. But for any other uses, I would say yeah, GIMP is as good as Photoshop. Again, experienced users are the most reticent: where the fucking sharpen mask is in this crap?
Things are different when getting into the server environment, there are people that knows better than average users, and average users usually don't notice which software is running in the servers, so no problem. A very marked point was when, after London Stock Exchange CTO said loud that, even if the most important stock exchanges around the world had already changed to open source because, well, RedHat and realtime trading, London was to remain with MS because they got full MS support. Then, the day Fanny Mae and Freddie Mac were going to the sharks, London Stock Exchange system crashed, and the full MS support couldn't make it to stand up again in time. So UK/european sharks didn't got their cut. AFAIK, that CTO got fired, London Stock Exchange has RedHat now, and I never heard of any other CTO saying they were to remain with MS no matter what.
I however agree with you in that time is money, and getting all the people proficient in a new software means a huge amount of money for a company, even if the features are there. Change will only happen when/if it makes sense crematistically.