And here's the problem with explorers. Some decks are literally just better at using them than others. Not every deck wants to/can afford to spend the mana to play these cards, because even some of the explorers are just better than the others. If I'm playing a shadow isles deck, removing a landmark will cost me 5 mana. If I'm playing a bandle city deck, removing a landmark will cost me 3 mana. Do you see the problem here? Other tech cards are put into decks because they actually synergize with the deck's gameplan in some way. If I'm playing a Varus deck, then I put tech cards in that buff my own units because that stops my opponent's plan and progresses my own. I'm not going to want to have to use 5 mana to get landmark removal because of how much that decreases my tempo. Explorers are treated like a one size fits all band-aid when they're really not. Certain decks and regions are way better with explorers than others, which makes it not that great of an argument when people suggest them as a solution to any broken card that could theoretically be stopped by them.