Article 5 is not long. It starts out with "The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all" People stop reading right there. Although the words "in Europe or North America" usually are replace with ellipsis (three dots). First error.
The major error is completely ignoring the last part of that SAME long sentence: "by taking ... such action as it deems necessary.

Though that's a good point, to me the key point is that article 5 has always been a bit of a bluff. Even if a massive intervention were deemed necessary, it was (ahem) always more than a bit unsure that a member with a big stick would actually wield it. This leads to my prediction: Mr Putin will have substantial success killing off NATO by calling the bluff, brief and repeated attacks on small NATO countries after which nothing happens in retaliation other than some strongly worded press releases.

That being said, I have no truck with those who say NATO shouldn't have "expanded eastwards" as it was a provocation. It wasn't NATO expanding, it was countries asking to join the club: that's how a new member comes to be. All the existing members did is agree to the applications, it wasn't a grand plot by a cabal sitting around a bit compass rose in a secret bunker. By far the most succinct explanation of what NATO is and does is simply "the club of places that would really rather not be invaded by Russia". It's inevitable that countries near Russia, especially smaller ones, will see the attraction of making the request.

Jim