Again, a different definition gives different outcomes. There is no good or wrong definition, but a definition where one has to look at all the cards in a specific format is definitely one that is not one I would advocate. First of all, you do not know the environment.
There is actually a pretty widely acccepted definition of power creep as it pertains to card games:
https://mtg.fandom.com/wiki/Power_creep
To paraphrase: "Power creep is [...] the gradual unbalancing of a game due to successive releases of new content."
Second, a simple example where your definition fails:
A format with a lot of 2/2 for 2. A few 3/3 for two. The tier one would be the 3/3. However, changing the 2/2 to 3/2 would change the power of the format without changing the top tier. So there is not your power creep but it will play a lot faster.
In most formats a four mana chimney would still be bad, but would a 3 mana one or a 2 mana one, or one, or 0? At least the Wikipedia one is consistent. Each time it is power creep. Would it matter most of the time no, but that depends on the format, which 1) you do not know, 2) in a format a card that becomes stronger on its own could actually become weaker. So your definition is not wrong, it is just inconsistent and depends on all the other cards, which makes it also inconvenient.
So, for me these two paragraphs are at odds with each other. In the first one you claim that changing the 2/2 to a 3/2 isn't power creep, while in the second you say that every time a cheaper version of Chimney Imp gets printed, it
is power creep. I don't agree with this second notion. Making Chimney Imp cheaper, isn't power creep, until we get to the point where the increase in Chimney Imp's power level leads to an unbalancing of the game. The reason it is absolutely vital to look at the bigger picture when talking about power creep of the game as a whole, is that it's possible to push the power level of certain areas, while artificially limiting the power level in other areas, so as to create new and exciting cards, without unbalancing the game as a whole. You get this state of flux where different areas of the game alternate in power level, without the floor being raised all the time.
I get the feeling Velrun is talking about this kind of power creep, which concerns the overall power level of the game, and you are looking at more isolated parts of the game and putting the label power creep on it. For sure, we can call a creature power crept if it outvalues everything that came before, because that does raise the floor of the entire game, but when looking at making weak cards strictly better in a way that doesn't impact the broad scope of the game in their particular niche (like printing a Chimney Imp for
), we can't call that power creep imho.
