NewNameNigel I can see what you mean about not wanting to group issues together and to take them case by case, which makes sense.
I do sometimes have to stop and interrogate my own thinking on these issues as humans naturally look for patterns and so it's easy to spot similarities between some of these things.
As you say, companies advertising using transwomen is one of those areas where there might be circumstances where I don't personally find it an issue (depending on the person, product, messaging, etc). I originally thought "does it matter if DM is advertising beer?" But because of the nasty way DM parodies being a woman (regardless of whether it is supposed to be self-deprecating, as that's kind of worse), I find that damaging and inappropriate of the beer company, whereas if the trans person was this proverbial "normal person just trying to live their life" we keep hearing so much about, then I probably wouldn't have seen it as an issue, as people with gender dysphoria obviously drink beer too. I don't love how companies exploit people's gender distress by promoting it as cool and trendy either, as parents are struggling, kids are struggling, medical professionals are struggling to deal with all of this ethically and responsibly and I don't think the corporates are helping (not that they care).
On pattern-spotting and grouping ideas and behaviours together, I do think that's helpful for women's rights. It's only when we zoom out and look at women's experiences as a whole that we can recognise systemic oppression occurring at the level of biological sex. And that helps us to point to it, organise together as a class (women) to discuss it, object to it, and push for laws to eradicate it and to protect women on the basis of sex.
If it weren't for pattern-spotting, it would be much harder to help women, say, in domestic abuse situations or to even recognise that they might be in one. This is just one example of many where pattern spotting works to keep women safe(r).
I agree that some people jump straight to "this is terrible" when the thing seems innocuous, and from what you've said, I sense you've probably behaved similar to me and asked "but why is it terrible?" and been lambasted for even asking.
But I think it's important to keep asking why and playing devil's advocate (not in a trolly way, but to drill down to the real issues) and stress-testing one's own views on the issue, regardless of the occasional accusations of being a TRA-sympathiser, because the last thing anyone needs to do is adopt a viewpoint they either don't personally agree with or can't fully articulate to others (which can obviously look transphobic if someone says they don't like this transwoman being used to sell x, but can't explain why other than saying it's because they're trans).
It was when I was still (very actively) inside the LGBT community and started seeing the gender identity rhetoric shift a few years back that I started to think "hang on a minute, does this actually work for gay people and for women?" It took me a long time to work out what I actually thought outside of all the emotional pulls and accusations in both directions (including believing I was agender for quite a while, as that what I'd been told, and it was the only way I could reconcile the belief that everyone has a gender identity with my own experience of not having an inner sense of gender).
Wherever one stands on gender identity, I think it's important to be able to question things and be able to debate them, as it's only when we are free to speak openly and honestly that we can get to the bottom of the issues and find a fair solution.