Standards have definitely fallen. My next flights are with QR, NH and CX. From recent experience, all consistent and offer a better product usually at a much lower cost.
I have recently flown QR J for 4 sectors. I found them to be better than SQ J in seating (except on QRs old ex-CX planes, even then, sleeping experience was better), food, service, lounge, amenity kit, pyjamas. The only thing I still prefer is to transit at SIN than DOH even though QR Al Mourjan lounge is much better.
I found SQ J catering standards to have come down.
However, for Aus-East Asia routes, SQ is still one of the best ones, and that actually provided some award availability to/from Australia in peak seasons. No way I would travel on QR via DOH.
CX is even more stingy on award availability, unless you are Diamond or above.
Of course i am not going to even talk about QF.
So really SQ is still a preferred airline, but on a least worst basis.