But isn't building an effective deck part of the "skill" in CCGs in general?
No, because since the dawn of language and communication people share ideas. And in Gwent, people netdeck. And that includes the very best players in the game like the Masters finalists so - just in case - please hold on to your "netdecking is for losers" comments.
It's no more braindead than any other netdeck or OP combo (lippy, traps, SK warriors, viy, NR poop swarms, etc)
Not true. Example. In traps, you gotta know oppo's deck and use your traps and commit accordingly. Warriors got specific dmg amounts bound to specific cards and board states - that got to be reserved for specific threats, so you gotta know the lineups. Warriors also gotta know about round control because sometimes it's better to go for long round, actually. NR is simpler as engine overload but you gotta know oppo's control capacity to plan your engine deployment; and you gotta bait removal. All these decks, you gotta manage resources.
In clog, your one and only "skill" requirement is for the opponent not to draw for R1 and let you win it it not matter what (except committing Kolgrim.) And not to throw the game forgetting about adrenaline and stuff. Same as Lippy but double the frustration because clog also messes up your draw. No resource management, either. You just gotta win that R1, get good RNG points on Mentors and dodge removal for defender and Kolgrim. Clog doesn't even care if you bleed all wrong and lose a card. If Kolgrim sticks, it doesn't matter.
And it doesn't mean that anyone who beats you with a strategy you don't particularly like needs their cards nerfed or their intelligence insulted.
You seem to have misunderstood the sentiment. It's not a critique of the players. I think one of the highest NG MMRs ever done was on clog (by Myamon, iirc, and nobody is ever gonna call that guy braindead when it comes to Gwent). I played a fair share of clog, myself. I wouldn't be criticizing it if I didn't know it.
It's only a critique of devs' priorities. Yet again, devs are nerfing NG mainstream stuff (for NO REASON as NG was <50% winrate LAST SEASON - it even rhymes) and promoting some memes. Just let NG be NG. The control faction balanced to keep greed in check.