apushutayid- The opinion of most rishonim and the shulchan aruch is that most eiruvim today aren’t kosher. Thus, by relying on other rishonim you are relying on a kula. The math is pretty simple. I’ve actually spoke to a rav who is a rav hamachshir on an eiruv and he said the same thing. These rabbonim might tell you that it is a kula that we can use,especially because the minhag has been that way for some time now, but it is a kula nonetheless. As for your koach diheteira adif argument, are you kidding? Of course as rashi points out being makil on something is more impressive than being machmir, but does that mean you can just go lekula anytime you have a shaalah?! On the contrary, rashi’s entire point is that it take so much more knowledge to be makil than to be machmir, so he’s actually saying the opposite.
iyhbyu- “I’m no expert in eruvin, but I’m pretty sure that everyone agrees to the concept, seeing as there is a whole mesechta in shas about it. ” So what you’re saying is I don’t know the facts, but I know I’m right and you’re wrong.
a woman outside bklyn and haifagirl- The poskim only talk about maaris ayin on fake milk with meat, there is no issue with having fake milk after meat.