Having played with
serra angel in an environment with old cards, the incremental advantage you got from it in comparison to another fair deck was just as big as a
grave titan is now. Sure, the bar is moved for creatures, especially 4+ drops. A big reason for that is that in older magic, expensive creatures were giving a mostly linear increase in power from low drop spell. This made 6-7 drop creatures worthless trash compared to efficient spells (especially
efficient non-creatures), and now they're playable (because you need incremental gains from every bit of mana you spend on a card).
If a 1 drop spell easily answers every expensive threat, then expensive threats simply cannot exist. I'm not really a huge fan of
wurmcoil engine because of the colorless bomb problem, and
grave titan is certainly on the higher end of power for 6 drops in any color or anything, but 6 drops have to do SOMETHING, and that's been true all the way back to the beginning of magic. That something-that-6-drops-must-do can be tweaked and moved to your particular power level of choice. That does not mean that grave titan ruins the game for every environment and it doesn't mean a cube with a grave titan in it does not care about incremental card advantage. There's a power level where aggressive decks see a grave titan and they can play through it. Sure, it is hard, but so is beating
serra angel with a bunch of old 2/1s. I personally don't run grave titan because its a bit above my power level, but I've played with it and against it in other cubes/standard, and you really are making a huge oversimplification of the card.
You talk in your other posts about aggro making a game not happen, which ties back into this. Your expensive cards aren't worth it against an aggro deck and it warps your whole format around it. Which is fine, but you've got to explore the consequences and compare instead of talking about 'power creep'. There are good reasons wotc did a lot of this stuff, even if neither of us may agree with them from time to time (but that's another story). Aggressive cards are also what keep a lid on the walkers.
Of course it changed how magic played, the only way not to change it would be to not print anything new.
Your skeletal vampire comparison is flawed. While I didn't play during that format, to my understanding it was relatively slow even for the era. It was right after a format that had Affinity, which made wotc attempt to power down standard at the time.
if you talk about power creep in magic, you are turning a blind eye to... let's just have a quick list off the top of my head of cards that are way the nuts compared to anything recent.