Easy wins may be fun for a while, but people get bored and drift away from a game if they’re not challenged and engaged. If any particular option is so much stronger than everything else, eventually people start to feel like they don’t have a choice – they have to use it. Particularly if the developers start balancing around that level of power. Then all the other theoretical options might as well not exist. Players want to win, but they also want choice and variety. They also want to feel responsible for their victory, to some degree. If you reliably win because of something you have, rather than something you do, then you as the player aren’t really necessary. The game then becomes something you poke for prizes, rather than play, but if none of those prizes have any chance of providing you with new and interesting options, then eventually it just gets old and people stop playing.
That fundamentally goes against the basic problem-solving nature of the player. Most people won’t have that kind of self-restraint, because it seems like fundamentally stupid behavior to not take any advantage available to you. We create games in order to give ourselves interesting problems to solve. If you have to deliberately play poorly in order to keep things interesting, then the game is fundamentally flawed. Players will choose the easy win over fun most of the time, and rightly blame the developer for putting them in that position.
Only because there are better options that are less situational. If everything was situational, then you’d have to think about what you wanted to use, and you’d see a lot more variety. Crafting a defense would be about running from the meta, rather than converging on whatever’s the most reliable, universal option.