I agree with you guys that at the end of the day the composite nature of the Satipatthana sutta is not a big deal -indeed most Buddhist texts we have are probably composites like this. However I don't think it's irrelevant. Having an understanding of how the texts we read evolved is important, and a cross textual approach allows to surmise which elements are earlier, or part of the original formula of meditation practice. This is not to attack or demean any modern practices which use later traditions or textual recensions (though some scholars do this) but to get a richer and more well rounded understanding of all dhamma practices and their history.
Reading Analayo's work has helped me immensely. It can get very complex and scholarly sometimes but its worth it because you gain a better appreciation of the text and how it all comes together. Also reading the Chinese Madhyama Agama version side by side with the MN version is very eye opening - I think its a good balance since I do agree with Sujato on this point which is that the Pali one seems to lean towards insight as its core practice - hence the expansion of the dhammas section and addition of the 'refrain' - while the Sarvastivadin Agama seems to stress samatha - including jhana descriptions. I also enjoyed Sujato's reconstruction of the Satipatthana Ur-text (or root text) and I think it makes a lot of sense here though at the end of the day these things are very difficult.
What matters here is that Buddhist meditation was and is a very broad tent and I'm happy to see scholarship opening up that tent.
Vayadhammā saṅkhārā appamādena sampādethā — All things decay and disappoint, it is through vigilance that you succeed — Mahāparinibbāna Sutta
Tārakā timiraṃ dīpo māyāvaśyāya budbudaḥ supinaṃ vidyud abhraṃ ca evaṃ draṣṭavya saṃskṛtam — A shooting star, a clouding of the sight, a lamp, An illusion, a drop of dew, a bubble, A dream, a lightning’s flash, a thunder cloud — This is the way one should see the conditioned — Vajracchedikā Prajñāpāramitā
I have seen all things that are done under the sun, and behold, all is vanity and a chase after wind — Ecclesiastes 1.14