The upgrades to BladeForums servers/hardware were necessary/overdue. The time that it took do simple things, like login, go to various forums, etc., was taking too long. Hence, the upgrade(s) to the servers/storage/network/other. You will notice that the login and navigation is much more responsive now.
Upgrading the forum software was a judgment call. I can't speak to whether there were highly desirable features that the new version offers. I have experienced software that gets out-of-date enough that it can't be upgraded anymore. That becomes a death spiral, so owners/moderators are keen to avoid that sort of thing.
Understand that the people who run websites HATE to do major upgrades, either hardware or software. It leads to downtime, upset users, perhaps hoof-and-mouth disease. Not sure about that last one.
I'll be 70, next birthday. I HATE change. My favorite conversations begin with "What's new?" If the response is "Not much", a lot of tension goes out of that conversation. I've spent decades creating upgrades for my software and applying them from software vendors. Both ends of the stick suck.
Seems that Spark is doing a super job of fixing the seemingly missing features (much of which involves "it's over THERE now..." and guiding all of us through the usual morass of changes. There will, of course, be bugs. It IS software, after all.
I don't care for some of the changes, but they certainly aren't grievous enough to stop participating here.
I have no inside knowledge about the decision making that went and goes on here. I'm just speaking from some experience with computers and software.
YMMV.