Its a number of things, though.
First, I've noticed the quantity of "blank looks" from the server has increased.
I'm spending far more time searching for SS issues by printing debug messages.
Second, validation errors silently stop the whole page.
Finally, SS code sometimes just doesnt get executed, due yes to some legitimate issue running the SSJS or tge like, but throwing no errors I can see, either in compike or often in debug runs.
Now, I've been on this platform ... longer than you. Love your work with it, and follow. But I know what I am missing in XPages dev environment.
I really need much better coding-time warnings, especially to trap issues with SSJS and validation coding. Yes, I am intensely aware Javascript syntax is all thats checked right now. It doesnt compare with other language support in Domino.