Have you looked into this verse's translation anymore? You asked how I came to my conclusion. Here's how. It's a very interesting verse from a translation stand point. It's what caught my attention to your original comment about the verb tenses in this verse. As I understand it, there are no verbs or adverbs in the original text "Therefore if anyone is in Christ, he is a new creation". Creation is a noun, not a verb.
They are added for the sake of correct grammar, I suppose.
If anyone in Christ, new creation!
Is the literal translation of the first part. No verbs at all.
By inserting adverbs, pronouns (someone had to choose the tense/mode) it makes a grammatically correct sentence, but does it overshadow a profound point Paul was intentionally making???? A big fat firm, maybe in my view. That is why I mentioned the nouns in the verse. All the nouns are: Christ and Creation. Thus if there is action taking place (a verb) it's the person of Christ that's doing the action to the thing (creation) which is modified by the adjective (new), as I understand it. Am I wrong?
This is why I prefer the LEB. It's so easy to see the original Greek text within it:
17 Therefore if anyone is in Christ, he is a new creation; the old things have passed away; behold, new things have come.
The verbs you spoke of being active are: behold, passed and have come (perfect indicative). We should "behold" new creation from Christ is my view.