I don't fly SQ F as much as
SFO777 but manage a few trips each year.
I haven't noticed a recent decrease in catering (a few years ago there was with some of the medium haul flights reduced from 2 to 1 meal). Indeed there have been some (small) improvements such as redeye flights now explicitly providing both supper and breakfast options.
I also have generally had good luck with gates close to the SKL - mostly low A gates and sometimes B gates.
As for SIN security at gate I've also not had to wait more than a minute or so. Perhaps the OP is not good at picking which queue will be slow vs fast?
I do agree with some that there are a few airlines that have improved to(wards) SQ's standards in recent years.