Do you object to the statement that generics are equivalent to brands, or that they aren't?
There are a lot of things that go into medications, as you pointed out, and allergens are the most severe - and not dismissable! - differrence. When a drug goes out of protection, the company is only required to release the mechanism of action; they aren't required to release the bindings you mentioned, or the coatings. They aren't required to release packaging info, which can affect the ease of which an arthritic patient - or a child - can access medications. Bindings and coatings affect release rates, which affects how the medication interacts with the body.
There is a substantial difference between formulations and packaging that affects some drugs. This isn't to say name brand is always better, but that there are differences.
I'd guess that you do not personally have a chronic illness for which you've been taking a medication for several years - am I right? Is your experience with generics all second-hand, through your patients?
In the US, the common experience of sufferers of chronic conditions is that pharmacies switch out generics every year as they jockey for higher profit margins. These people will confirm that there are definitely differences between formulations that affect percieved effectiveness. Should we write this common experience off as imagination?