Has MEX really gotten that much more congested since WS last operated this route (late 2018) and had a very nicely timed daytime turn? Wikipedia says it handled 45.4 million passengers last year vs 47.7 million in 2018, and aircraft size has generally been trending upwards (aircraft movements down from 459K to 322K in the same years), so the slot thing isn't making a ton of sense to me.

I agree the timing renders this flight useless, and I'm puzzled why they chose to run it at all, unless the target market is primarily people living in CDMX visiting Canada and/or people living in Canada VFR in CDMX, in both of which cases the concerns listed here (while very relevant to many of us gringos) may not apply.

Like several others, I'd love to be able to do a long weekend trip down there, but will never take this flight as-is.