Oh so it's YOUR fault. ;)
Don't worry -- I came to love Cider for the simplicity. I tolerate Cider V, but its "anything" nature means it's not good at anything in particular. These days, I mostly use it to peek into what (Antigravity's internal equivalent) does.
I was in the Eclipse camp, prior to the IntelliJ reversal. At the time there were at least double the number of active daily users of Eclipse, Google had hired some original Eclipse devs who did an awesome job making Eclipse work at Google scale, and basically I was back to where I had been (in productivity) before joining Google.
The decision was made to go with Eclipse. Then it magically went into some sort of internal box/decision process, and came out IntelliJ instead. I've always thought this was because of a sufficiently highly placed Android person with a personal preference, but I could be 100% wrong.
This made me sad. I escalated internally, compiled all of the usage numbers, did feature comparisons on what actually worked in each IDE, to no avail. Near the end, Eclipse's C++ support and refactoring actually worked reasonably well on Blobstore, which was NOT a small thing.
IMO IntelliJ never worked very well in google3, and certainly didn't have anywhere near the level of fluidity and speed that Eclipse had (all the way back from its VisualAge Smalltalk roots -- something even most users of Eclipse never really understood or got into). That said, Eclipse just had the wrong architecture for a massive monorepo. It could be made to work (and it was), but it was never a good fit...and getting the upstream changes needed was apparently problematic.
Plain simple Cider was better (in my mind) than IntelliJ's broken functionality that worked in the outside world, but not in google3 (at least not on the code bases that I worked in).
Plain old Cider just kept adding smart features that solved problems and made it nicer. By the time Cider V was coming, it had big shoes to fill.
As someone who predominantly writes in Go, cider-v was a massive step backwards compared to cider. I eventually moved entirely over to using vim (with the set of internal plugins for blaze etc) which became so much more useful, but I still missed the features of a proper IDE that cider just excelled at.
I imagine a lot of it came from that push to "use outside world tools more rather than writing our own" which is great in theory, but really felt like a huge leap backwards in terms of convergence.