At this point, seeing behavior and responses like this in so many communities of my interests, I feel like even that gentle of an approach is still too much agenda-pushing.

Not that the agenda in question lacks for value, ethics, or good intentions, but at the end of the day, based on the newbies inquiry, it's still some version of, "You're wrong for wanting to explore your interest. You should do what I tell you to do instead."

In the communities for my interests that I participate in, I try (and sometimes fail, we're all human), to explicitly steer clear of doing anything to diminish their enthusiasm, curiosity, and desire to learn. That's the little ember that they need to really get going, so for me, the priority is not to put that out.

Especially in a case like this where, sure, maybe a native garden is ideal...but the alternative if they get overwhelmed or shut down or forcibly redirected by the community is probably just going to be grass and weeds, or no plants at all.

I think it's great to offer up the natives as an alternative (while explaining the benefits to both the local ecosystem as well as to the gardener), but I would also say that if you're going to do that, one should also encourage them to get into their new interest regardless of whether they follow that suggestion or not.

If OP wants to plant tulips, fantastic, and I'll give you any tips I can on how to do that. I may suggest natives and why they're also a great choice, but under no circumstances will I go into negative territory in telling them they shouldn't follow up on their interest, unless of course it's illegal, dangerous, harmful, etc.