Not at all. There's no shame in using what works, and everyone makes their own personal tweaks to their decks anyway. I have done it myself; Last month, before Feartrops was nerfed, I was running that deck in ranked for a good while. I ran into a player using 2DoD/1EX who destroyed me so I decided to copy the idea of the deck and make my own. I subsequently ran that in ranked and found myself getting a lot of wins because it was strong against most of the meta decks.
If you are making your own decks and messing around with idea's, stick to normal. But, if you are playing ranked and serious about reaching the top, you absolutely need to be running a strong, optimised deck to get consistant wins and, even then, you actually need to be skilled and understand the deck to use it well. Copying a top tier deck isn't enough on it's own. I've faced plenty of low ranked players that were running meta decks such as feartrops, tinkercide, mechborn aggro etc and destroyed them because they simply weren't that skilled.
I would say it is frowned upon. If you just continue a cycle of deck copying and improving upon the copied deck, then there is no innovation, and that leads to a dull meta of everyone playing the same thing.
"If you improve upon garbage, it is still garbage."
Not that deck copying is entirely your fault, because it is mainly Lightmare/Yodo1's fault for designing such an imbalanced game where favoritism is clearly shown towards certain deck types and factions. In my opinion it is bad form, but the developers have not left you much with a choice.
You are a thief. The pilot just sits there and turns on auto-pilot. The vehicle is everything. Once you reach the skill cap, the game is 100% RNG.
How do you sleep at night, you netdeckers!
"Hurr durr copy a meta deck to get easy wins, game is autopilot guise!"
Seriously man, you are becoming somewhat of a joke these days with your opinions. It's really hard to take you seriously anymore. I mean, I agree that Death Blast needs a nerf since it is currently the undisputed strongest deck and nerfing that alone would allow for far more variety of decks to be viable, but that's as far as it goes.
Oh, and, the huge puffying irony of your post is that you, at one point, stated that you were going to reach the top of ranked using "your own GI deck" which was, surprise surprise, just a variation of the old top tier deck, Valuebots. I played against you with my 2DoD/Ex deck and, despite using a top tier deck and using cards that made the matchup harder for me (disruption sphere comes to mind) I still beat you. You honestly just chat so much puffy. Actually follow through with what you said; get to top ranked and then come back with a valid opinion.