That's one way to play. Personally, if I knew the GM was secretly adjusting the game much I'd feel dissatisfied. Why not just give me a sticker that says "You win!" if I'm always going to win anyway?
Though this does tie into a separate bugbear of mine: D&D makes it hard to reason about encounters because the stats are unbound and all over the place. You see four bandits rummaging through the wagon they stole. Do each of them have 8 hp, 16 hp, 32 hp, 64 hp? Who knows! Do they attack once or twice? Could go either way! That is not an innate property of RPGs, but it's very common in D&D, and I think leads to a lot of "oh this is going badly - let me fudge the stats". Both because the GM got the math wrong, and because the players assumed these were 8 HP bandits and they're actually "well you're 5th level the bandits should be tougher" level scaling bandits.
I don't think the GM's job is merely damage calculator. But this:
I rather disagree with. If there's a plan then why are we rolling dice? I don't want to play to fulfill whatever the GM's plan is. They should just write a book. I've had many great, memorable, scenes that came about because the players had a challenge and they overcame it. Sometimes after running away and trying again. If I just decided "oh I guess the dragon's breath rolled really low" then, again, we should just write a story together. Or play a game that doesn't have such a big random factor.
Like, I also don't really enjoy a nameless kobold killing Finnigan the Fighter with a fluke natural 20 in what wasn't supposed to be high stakes. But the solution for me isn't to fudge rolls, but play a different game. I don't really like stupid deaths like that, so I don't play games that facilitate it. I know that's kind of "baby with the bathwater" for some people, but I really do think some people are fighting against what D&D trends towards, when there are better tools. It's a hammer. Sometimes you want a screwdriver or a pen.