Spikes = players who are highly competitive and keep up with the current meta-gaming ideas
Netdecking = pejorative term for creating a deck based on meta-game archetypes researched online/from more experienced players instead of solely through personal trial and error.
Netdecking isn't really about learning from other players. It's like calling someone a script-kiddy rather than a hacker. Someone netdecking would not be able to craft that deck on their own, and is not looking to learn the skills to do so from it. They just want something with a stable winrate that someone else has researched.
There are two aspects to playing a collectable card game[1] - building a deck (done on your own), and 'driving' the deck (playing your deck against other people). They generally correspond to strategic and tactical thinking; one tries to solve the problem of "how to win", the other looks to "what is the correct play in this particular instance".
Generally speaking, building a deck is considered _much_ harder to do, because the problem space is so much bigger. Coming up with lines (avenues of play that let you win the game), understanding the mechanics that create synergy, understanding how your deck interacts with other decks and how it answers (or ignores) various types of threats, how it addresses common issues (card draw, mana curves, late game vs early game strategies, etc), what to sideboard - these are hard things to do, especially in a game like Magic where there's a non-trivial number of cards rotating in and out of Standard. It's actually even harder than that, because there are multiple ways to win, so you have to add another layer above that.
Netdeckers focus exclusively on the mechanics of playing the game using a deck list someone else has come up with. It's a pejorative because a lot of times these players don't understand what they're doing, they just know "person x used this deck to win tournament y, and I watched a stream where they talked about how to play it". This is a bigger problem when playing in the Real World, because these players don't have an understanding of the rules/mechanics of the game that makes the deck "good", which is very frustrating to play with. They outsource a lot of the strategic thought and understanding of the game to someone else. They play very deterministically and don't know how to read the table/how to get a sense of what their opponent's deck is trying to do. You can get pretty far piloting a good deck, but you're never going to be _good_ at the game.
[1] I'm going to focus on Magic the Gathering because it's the most well known/popular of these, and is the most copied...because they've spent a long time learning these lessons the hard way.
It's mostly an attitude held by more casual players who don't want to spend money buying specific cards to play along with the current metagame. They see netdecking as either paying to win, which in some sense it is, in Magic: the Gathering at least, or just 'cheating' when someone assembles a deck from a list they found online.
People who play magic more competitively definitely do not have this attitude and spend a lot of time experimenting with the meta, and reading about it and the deck archetypes for the format(s) they play in. Including tournament winning deck-lists.
Because it only leeches from the collective pool of knowledge / experiments, instead of experimenting and trying different things which could lead to diversity. Some people won't have the time to pull off experimenting though, and it is also possible to get inspired by someone else their deck. It is also a form of jealousy/spite by those who do spend time; as they see other people who spend (far) less time in the game, to overcome challenges.
For me, I am a former MtG player (mostly end 90s), and the game is 100% P2W, as is Hearthstone. I enjoyed the orig. SWCCG a lot as it was very different, but it also was more... weird and roleplayish like. Other than that, Micropose's 1997 MtG was buggy (hehe and put off turbo button to make game speed go down) but at least also somewhat fun, and allowed players to play with old cards for not much money. The only other CCGs which are not P2W are Netrunner and Slay The Spire (inspired by Netrunner and not really a _C_CG but rather a card game with rogue-like element; it does have the arena/deck building aspect to it though!).
Because everyone running the exact same meta is a very boring game. Instead of each game being it's own unique battle, it's the same battle ad infinitum.
It's more of a "You're not good enough to do anything but copy others" sort of thing. Tracing a Picasso will give you a pretty piece of art, but it doesn't make you a legendary artist.
Most people don't care that much, but you can also see issues if the community is mostly all copying the same 3-5 people's strategy, since that makes the game feel samey and boring.
In chess the beginning of the game is called opening.
Its a set of pre-calculated/analyzed moves that lead game into different type of positions (styles of play).
It would be madness to call people who use 'openings' lazy etc.
It's literally how the skill levels of given game are improved. If something works, use it, then improve it/evolve it and lift the skill cap of the game up.
What does this mean?