Every announcement you will read about a game is a marketing document. That is not a criticism of the people who write them, it is what the format is for. But marketing documents contain verifiable facts mixed in with claims that cannot be verified, and separating the two is straightforward once you know which is which.
Facts, claims, and vibes
A fact is something you could check. The date, the platforms, the number of playable characters, whether a feature is in the base game or behind a pre-order. Facts in announcements are usually accurate, because being caught lying about a fact is expensive.
A claim is a statement about quality or magnitude. This game will be revolutionary. This is the most ambitious project in the studio's history. These are unfalsifiable in advance and meaningless in hindsight, and no amount of careful reading changes that.
A vibe is everything else. Art direction descriptions, tone, the emotional framing of the trailer. These are opinions and treating them as evidence is the mistake.
The pre-order boundary test
When a feature is described as available to pre-orders only, that is a hard fact about a business arrangement, and it tells you the feature was not in scope for the base game at planning time. This is not necessarily bad, but it is information: the game you are buying on release day is not the game that was described to you.
Count these across an announcement and you get a reasonable proxy for how much content is being held back for a later purchase or a later year.
Trailer length as a signal
A two-minute trailer showing gameplay is worth considerably more than a four-minute cinematic with a montage of different games at the end. The latter is a genre-identification reel and tells you the publisher is selling you the idea of the game rather than the game.
CGI trailers deserve the same discount. A fully rendered trailer does not demonstrate the game exists in any playable state, and studios under financial pressure are more inclined to produce them.
What to wait for
The most reliable information about an upcoming game arrives after the announcement, in three specific places: a hands-on preview by a creator who was given early access, a demo or playtest, and the first post-launch patch. Each of those is harder to spin than an announcement because it involves someone else experiencing the actual build.