The Beluga Sanctuary has its issues, but most have been out of their control and they've proven to be proactive in prioritising the welfare of their animals even when it loses them money and damages their reputation. If you think that is a "not much better" outcome for these whales compared to them literally just dying, then you need to do some soul searching as to why ¯\_(ツ)_/¯
One could argue that perhaps you're the one who needs to do some soul searching - is it really better for these whales to be in this "sanctuary" than to simply have a humane, pain/stress free ending and just not exist anymore? There is absolutely an argument to be made that this is all being done for several reasons not involving the best interest of the whales.