But couldn’t one also say that power creep erodes restrictions and, therefore, erodes creativity from the players?
One could - but given that the players have an infinitessimal range of options compared to the DM I don't consider this much of a problem unless we get full 3.5 wizards back.
Sure but if you're in the trenches running a game and a player comes to you with a new build, and you're building encounters correctly and using monster manual critters and suddenly you realize that this guy is doing more damage, taking less damage, and seems to have no particular weaknesses, it's ok to be like "now...hold on a minute!".
If the expectations of design have changed, and you haven't been given the tools to deal with the change, or really, even a heads up, that's no good either.
The problem with this statement is that even if it's true it's in my experience largely irrelevant. The majority of the most broken options in
any edition are in the PHB when the material is understood least well by the designers. Yes, they can be broken slightly further with additional options but the reason the 3.5 Incantatrix prestige class was broken wasn't that it could play games with metamagic - it was that it took what was already the most powerful class in the game (wizard) and then made it even more powerful. And yes, the Incantatrix in both 3.0 and 3.5 was an
actual example of power creep that took the most powerful options in the original game and made them even more powerful.
Meanwhile a lot of DMs complained about the Tome of Battle/Book of 9 Swords. And it really did lead to many fighter players "doing more damage, taking less damage, and seems to have no particular weaknesses" compared to the baseline PHB fighter. Of course there was a reason for that - the baseline PHB fighter was an awful class in 3.5, especially when not put together with obnoxious and spammy gimmicks like the spiked chain trip cheese (which still wasn't in the league of a wizard). The normal agreement is that the PHB Fighter is Tier 5 (i.e. awful and at best a one trick pony with major counters) and the Warblade Tier 3 (i.e. decent at their job and with some flexibility). Meanwhile it wasn't either a wizard or CoDzilla.
The expectations of design had not changed. What changed was that WotC were now trying to put something in there that was in line with the expectations - and people were comparing it to something that fell massively short.
And WotC is usually pretty slow to print DM-facing content because it doesn't sell as well (there's more players than DM's).
They will change design goals, and print better player-facing options and then be like "oh yeah, I guess the old monsters need an update, here's your MM3 or Monster Vault: Threats to Nentir Vale".
WotC really messed up monster scaling - and skilled players
using the PHB alone had demonstrated that pretty much since launch. 4e was really rushed out of the door. It was given a 2 year development cycle and they went back to the drawing board ten months in; it really needed another year of playtesting and polishing.
Whether being able to sell a book that requires you to buy another book to deal with the options in the first book is reasonable is a whole other discussion in of itself.
How about selling a book that tries to fix the flaws in the original book?