I was talking about individual matchmaking and it doesn't matter if you can blacklist a faction, deck or player because the principle remains the same as well as the inherent problems I've explained in my post.
Let me go through your points then.
1. A ban/reject mechanism is the wrong solution
Like I have explained, banning/rejecting a faction is not a good solution and it's only being suggested because some decks are far too common (and either annoying, OP or both). Banning a faction is like putting on a band-aid, instead of properly treating the wound. We have to look further and deeper. Because, if we don't, and we continue to band-aid everything, the game will not improve. If we accept such a solution, it sets a wrong precedence for Gwent.
So it seems the untreated wound is better than a band-aid, because for months there has been no improvement. It actually keeps getting worse. If more netdeckers is considered a game improvement, then I think I'm totally confused.
Setting wrong precedence? It's not necessarily wrong when you think it's wrong. It might as well be good, but we won't know until we try it.
2. A ban/reject mechanism can be exploited for other purposes
Every player can just ban the faction or reject the match-up their deck is weak against, creating an unnatural win-rate. Furthermore, they can actually start optimizing their decks, knowing they will never have to face X faction for an even higher win-rate. Ironically, the opposite can happen too, when players do not optimize their decks, they might no longer have a favorable match-up (because others ban such decks), which might actually lower their win-rate. This doesn't create a balance, instead it creates more polarization. To put it bluntly: it makes the strong stronger and the weak weaker.
This does not seem to be a valid point for blacklisting a netdeck. Simply because with one blacklist you could not ban all the netdeck variants (e.g. modified by 1 or 2 cards). It would take time and a lot of matchups against those to filter out enough of them to be even close to consider this option as faction ban, or to consider this mechanism a sort of abuse for unnatural win-rate improvement. You might ask - then what's the point of the blacklist if replacing just one card in a netdeck will not be preventing matchups gainst those. Well the point is, if player A faces player B using netdeck X and blacklists it, then unless B modifies X to be X1 variant, A won't be matched up with B using X. If player C uses the same X variant, or X1 (which would mean that either C copied it from B, or came up with the exact same modification idea - which btw. has a lower probability considering the amount of available cards), then A won't have to face C, and so on. The outcome of this would be:
- unmodified netdecks get filtered out by matchmaking for someone, that blacklisted it - meaning the number of repetitive matchups are decreased significantly, as most people don't bother modifying the netdeck even by 1 card, which I find especially shameful
- modified 'netdecks' - player A would need to still play them, and if decided to blacklist, then the same variant of netdeck will be filtered out from now on
- netdeckers would start modifying the decks they've copied (which would hopefully develop their desire to explore the deckbuilder), or leave them be and play only against people, who don't mind facing the same stuff all over again.
Would that lead to situation where, how you put it, the strong become stronger and the weak weaker? I'm not sure, but but currently the role of strong is assigned to the netdeckers, and the weak to the ones homebrewing their decks and experimenting.
3. A ban/reject mechanism makes the meta worse
Because of the above (point 2), it also shifts the meta into a weird direction, creating decks that should normally not be able to thrive. At first, you might think that this promotes variety, but at what cost? You are getting super-optimized decks that can run rampart, which exacerbates the issue a ban/reject mechanism was meant to solve.
Having in mind, that blacklisting would be only for unranked matches, I dont see such danger. People playing for fun, would have a bigger chance to enjoy the game, and for people playing competitively/rank, nothing would change.
4. A ban/reject mechanism will punish players unjustly
Furthermore, as mentioned by Draco, it punish players unjustly (i.e. creates too much collateral damage) because there is a major flaw in implementing a ban/reject mechanism. What about those players that are actually trying out a different deck (home-brewed or otherwise)? Can you spot those? No, not always. So, if Nilfgaard does get banned by everyone, for example, then that means that no one can make another non-meta NG deck. Thus a ban/reject mechanism actually adds more fuel to the fire, instead of less.
This is totally not the case, which reply to point 2 is clear about.
5. A ban/reject mechanism might be hated more (then what it tries to solve)
The last reason is somewhat of a paradox. But, if players truly want to have fun (i.e. chill out) in casual, then they shouldn't play (annoying) meta-decks. Yet, this is still happening. So, players have another idea about what casual should be. Because of this, we should be careful with changing casual. I don't know how many people are annoyed by faction X, but it may very well be that more players will get annoyed when their faction gets blacklisted.
Again, the blacklist I'm thinking of is a single deck oriented and made by an individual for an individual. Blacklist made by player A for deck X would not prevent player F from facing deck X unless F decides to blacklist that one on his own.
As for your point here, I also don't know whether more people in casual mode prefer to be netdeckers or are annoyed by facing those, but which variant is better:
1. having some % of players being happy netdeckers* and some % of players being frustrated of facing the former, or
2. having some % of players being happy netdeckers* and some % of players being frustrated of facing the former but having the means to reduce their frustration?
For me the choice is obvious.
* we also can't really tell if majority of them are not the type of people following the "if you can't beat them, join them" rule
6. [Bonus] No other CCG has done this either because of good reasons.
It's like saying cow dung must be tasty, because billions of flies cannot be wrong.
And to sum it up, I won't die for the idea of blacklisting, but I really do think it would be a good option to have a choice, because otherwise the situation will definitely not improve.
Edit: oh, and by the way, isn't it interesting, that in Gwent tournaments the participants ban one of the decks of their opponent? If it's not bad there, why would it be bad in casual modes, where the fun and not necessarily win-ratio should be the most important and tempting factor.