All other airlines I had booked with for my April trip who have cancelled flights (Vietnam, Cathay, Air Asia, Thai) have agreed to a full refund of the cost of flights. It would of course be Malaysian that is the exception.
I've just had the same experience as the OP. After MH had changed my booked flights BKK-KUL-DEL-KUL-BKK about 6 times, they finally cancelled them all. When I finally got through to their call centre I was told that, despite the fact that my entire itinerary had now been cancelled, the only option was a voucher, which has the drawback I mentioned in another thread, that it is only usable through a call centre (at significantly enhanced cost) and furthermore is only valid until the end of the year.
The call centre operator's line of reasoning was that the flights hadn't been cancelled by the airline, but as a result of the COVID-19 pandemic, therefore Malaysian had no obligation to refund the flights. Clearly nonsense, but she had her script and wasn't departing from it. I've seen on other threads here that a better result can be had by phoning the main call centre in Malaysia rather than one of the outstation call centres to which international enquiries are routed. Is that still the case?
And if that is no longer the case, presumably I can now request a charge-back from my credit card company?