The Reagan White House moved to lower tax rates for developers in the 1980s and then years of low interest rates glutted downtowns with office buildings. Time's up.
That's one of the biggest factors for me, too. Of course the elite want to blame it all on WFH, but there are plenty of people who would still go to downtown areas to eat and shop and go to bars, but who the hell can afford that these days? If wages were even close to keeping up with the cost of living, I'd guess there would be more downtown activity.
WFH does has some effect on people going out. Personally, I have the financial means to still go out on occasion, I just don't. When I used to have to drive in for work, I would eat lunch out about once every other week (I have an old, bad habit of treating myself to lunch on pay day). That's a sold meal which is now gone from that area's economy, and I'm sure there were a lot more. Beyond that, I find that there is now a greater mental barrier to the effort required to get dressed up and go out for a meal or shopping downtown. I'm like Professor Farnsworth from Futurama, "well, I could go out. But, I am already in my pajamas."
That said, ya it's not all WFH. Even with the financial means to go out, the current economic environment means that I'd rather not spend $100 eating an over-priced, poorly cooked meal somewhere downtown. I can spend $50 on some really nice ingredients, grill up a couple steaks, cook vegetables which aren't overcooked to be limper than a eunuch's dick and eat potatoes which don't taste like they came out of a box. The other $50 can go into savings and I don't face social pressure to put on real pants.