My 2 cents with SQ:
1. SQ's CEO is a joke. So I am not surprised in the declining service. The good news - the CEO is not stressed by the shareholders as a flag carrier.
2. CX, SQ's competitor in Asia, declines way much faster. There is no incentive for SQ to improve so long it is above CX.
3. SQ's Ground service is non-existence for the entire world. AFAIK - SQ outsources its own ground service to a subsidiary - SATS.