There is great evidence that Tosafot were trying to justify local minhagim, many of which do come from the Yerushalmi, Tosefta, and masechtot ketanot, with the Bavli, whose authoritative nature did not necessarily take root in Ashkenaz in the same manner as it did in the Sephardic world. Just consider the pilpul of Tosafot versus the straight-strict constructionist approach of the Rif, let’s say.
The mehalech laid out in Rambam’s Hakdama le Mishneh Torah informs my view of what proper halakhic methodology ought to be. Hence my not using eruvin on shabbat, and so on.
The approach of Tosafot is very similar to how the CJLS determines its “halakha,” though. I understand the mindset which motivated Tosafist innovation. Whether it affirms the authority of the Bavli and the significance of hatimat hashas is another matter entirely. Although much poopooed by R’ Hayim Soloveitchik, Talya Fishman’s new book does address these questions of textuality and authority in Ashkenaz quite nicely.