All that you describe is the result of increased competition especially from budget airlines. Costs have had to be cut because the vast majority will book a flight $20 cheaper without any thought as to quality.
One can buy LHR-BKK-HKT return for £510 at the moment yet 15 years ago the cheapest was about £450, what else has gone up just 10% in 15 years? Rail fares? A flexible ticket with 100% miles is £992.
Silk Air is 100% owned by Singapore Air and even if you booked direct with them and your ticket has an SQ flight number you won't be allowed in the SQ lounge with a SA Gold card.
I do though agree with you that this is short sighted and alienates the good customers, SQ have lost my business due to this but they might get some back between now and late October as I just can't stand TG911.