Not necessarily. Maybe it's wrong of my GM not to provide opponents that can't be turned into "cakewalks" by the use of one spell.
The entire point of the GM is to provide interesting challenges for the players, and you keep saying, "Well, what if the GM doesn't provide a challenge? Isn't it a problem that the game isn't a challenge?"
You can look at it as poorly designed rules. But it also can be poorly designed encounters.
If you WANT big magic with save or die/suck as part of the powers and threats that exist to be controlled, avoided, and overcome then first the nature of the adventures should take that into account.
Yeah, I think both of these situations are ones that a good DM can, of course, avoid. But I think that can be a problem in and of itself - if the game requires a certain level of system mastery on behalf of the DM in order to be enjoyable.
Especially as you get higher level. At level 1, you've got one spell for the DM to worry about - Color Spray. Soon you add Glitterdust into the mix. And buff spells, and divinations, and more - and by higher level, in order to properly 'challenge' a high level wizard, the DM might need to spend hours of optimizing on their own. Or resort to blanket solutions like sticking the wizard in an Antimagic field - and while that might be interesting
once, it could get real old, real fast.
Now, that isn't to say that every game will require that level of planning to avoid a caster overwhelming it. Nor is it to say that some groups won't
enjoy that level of one-upmanship. But I think for many, that it is part of the problem.
At the very least encounter design should realize what makes an interesting activity for the level of power in question. Obviously you could get into a whole long discussion on this tangent. But, without getting hung up on "best", I think the Holy Word spell does a perfectly fine job of doing what it was aimed at. It may be that what it is aimed at and what this given set of players want are different, and it may be that the encounter designer failed to account for the implications of the power level.
It certainly still comes down to a bad overall play experience in the example, no doubt. And I'm not trying to claim your explanation is wrong. But depending on your tastes, completely different explanations may apply.
And just to be clear, again, I wasn't necessarily using that as an example of the imbalance in the system. It
is something that could have been addressed with different encounters or characters. My main point there was that it was an example of the spells and powers presenting this sort of imbalance without any optimization or powergaming required.
The character was a Cleric, and took an appropriate Domain spell. In this situation, it trivialized another character's participation, and largely incidentally. This is a thing that could happen, and it could happen without anyone
setting out to build the guy who always 'wins', as Jeff Wilder had suggested.