> annex [verb] - add (territory) to one's own territory by appropriation

I don't think anyone supports NATO annexing countries, problematic or otherwise.

That's one definition, use the one that makes sense in context:

https://www.merriam-webster.com/dictionary/annex

I was expecting a retort of more substance after I answered your question.

The issue is that "annexing" has already a precise meaning in the current Russia-annexing-territories context!

[Your use may be acceptable. But Google finds no matches for "annexing into NATO" and only a few for "annexation into NATO".]

Well if it's acceptable and you understand now, care to reply to my response to your question?

What would you want me to say?

1) In response to Russia's invasion of Ukraine, you think that action A should be prefered to action B if the latter will be perceived by Russia as more aggressive - increasing the probability of a of a declaration of war by Russia.

2) If Russia was to invade Sweden - for example - I imagine that you'll find that action A2 should be prefered to action B2 if the latter will be perceived by Russia as more aggressive - increasing the probability of a declaration of war by Russia.

3) If there is Russian attack on a NATO country you see war as a consequence.

Some people think that taking action B now may actually decrease the probability of finding ourselves in scenarios 2 or 3 later. Maybe you don't, or you think that it increase the total risk.

But at least we may all agree that to minimize the probablility of war you have to consider the whole sequence of potential events.