Well, I said "might not be" because that's a whole other discussion, and I don't have all the facts.
I totally agree about web technologies being the way forward though - if you ever read one of those "MMF3 wishlist" threads from 15 years ago, you'll see C3 ended up being pretty much exactly what I was wishing for even back then (I've been using Clickteam products since Klik n Play).
I have absolutely no doubt that sooner or later, most software will be built using them (cutting edge 3D games being one of the few exceptions). The web has better GPU hardware acceleration than CF2.5 (WebGPU being based on DX12/Vulkan rather than DX11). Ignoring WebAssembly etc for now, Javascript is undeniably slower than a compiled language like C++, but only about 8 times slower, and modern hardware is so fast that it really doesn't matter (my 2020 smartphone is 4-5 times more powerful than the 2015 laptop) - even if it's not the fastest, it's fast enough. Being able to leverage the Javascript knowledge that I already possess would be huge - whereas extensions in CF2.5 are a mess, and have to be rewritten for every runtime.
Many popular productivity apps like the Google Office suite and Canva are already built as web apps. I think the reason that games of the kind made with CF2.5 (casual, 2D) haven't followed suit is that they are only really played on mobile devices these days, not PCs - and Apple have done absolutely everything they could (including breaking any and all regulations) to kill web apps. In fact, Apple are back in the news again this week, for this very reason - Please login to see this link.
I understand the reason for making C3 subscription based, but it doesn't mean I have to like it! There was a similar backlash against Adobe's Creative Cloud. In fairness, a £105 per year subscription, while expensive compared to CF2.5, is still pretty cheap as hobbies go - I spend more than that in a month, playing badminton.