Meditation is not immune to needing the scientific approach. We should label which types work and which don't work, so we can understand it and make it better.
That's not stopping you from doing whatever you want.
Your use of the word immune speaks to the degree which scientific concepts are applied out of context. Good luck grasping meditation concepts with an empirical approach, what will be the dependant variable? There is no point in labelling "what works" because it will be determined by who is using the technique and who is guiding them.
I think it's useful to reach conclusions like "most beginners flounder with Zen but make fast progress with Mahasi noting". But there are always exceptions and some individuals seem to benefit from less common approaches.
Sorry but no, under this guise any esoteric, homeopathic BS can gain ground. Effects of meditation, too, will have to either be objectively measurable. If they were not, it can be dismissed.
It's not medicine. Do you do null hypothesis testing after you pray? Some things just aren't objective - see psychiatry for an example of a super scientific approach to subjectivity. It still generally results in BS homeopathy that doesn't work.
the curse of causality you mean. it's hard to isolate the causes of things, but you have to do it, otherwise you don't know what works and you're drinking cow piss to prevent COVID or saying vaccines cause autism