I get what Gadol is saying. I personally do say shehem mishtachavim (sorry I can’t type in Hebrew on my computer) in the aleinu, but I skip that Aramaic line the Artscroll has in parentheses in the last paragraph of Az Yashir. I would understand wanting to find a siddur that omits what you omit and includes what you include, but there are many permutations; it’s not just a matter of Sphard vs. Ashkenaz.
Another good example would be the infamous gray paragraph Artscroll puts in benching, complete with a lamentation about how nobody says it anymore. I’ve never met anyone in my life that actually says that paragraph; I’m convinced there’s just one editor down at Artscroll that’s really passionate about it.