"At this point" does a marginally faster CPU make a big difference? Not to me, my "workhorse" laptop is a 2013. But if they stuck with a 2013 CPU in a 2018 Macbook, people would go ape shit even though for people like me, the faster processor doesn't change a single thing about how the machine works.
Way too often people on here see something and think "that doesn't help my use case, therefore it's a stupid decision" and never stop to think "hey maybe someone has a use case I don't have, and maybe this helps them". To you, 3mm doesn't sound like a lot. To me, a few hundred Mhz or another few GB of RAM doesn't sound like a lot. But you don't see me screaming in the comments thread "how dare Apple put a faster processor in their Macbooks instead of shaving off another few MM of thickness!" because that's just ridiculous. Someone out there is happy that the machine is faster, even if that person isn't me. I have the ability to put myself in someone else's shoes and be happy on their behalf.
Some people's laptops sit on a desk all day and that's fine. Mine doesn't, and every MM shaved off is another pair of socks I can pack into my luggage.