If you need to be forced to think of new strategies, then you're just not trying hard enough. Even when playing the same person over and over again, either you're not getting any better due to your inability to brainstorm, study, or simply experiment with new stuff, or the game has little depth and you shouldn't waste your time with it. There's a lot of resources on SmashBoards to learn from so that you can improve your game, and the number of options that most characters have in Smash games in general is staggering. It takes a lot of self-analysis to get significantly better; general experience will only get you so far.
As far as getting better goes, they have to -want- to get better. If someone gets angry because I give them good, general advice (trying using N-Air out of shield more when people pressure and see what happens, make use of safer moves, etc.), then they don't have the right attitude, and will not get better. That's just helpful advice from a competent player, and if a person doesn't want to even try to figure out what to do (and what not to do), and give new tactics a shot, then they're not concerned with becoming better players. I agree that being helpful, friendly, and positive are very important in making other people become more receptive to the community (and, therefore, making them play the game), and having people of relatively equal skill level helps with motivation more often than having a bunch of people who dominate, but it still varies on a person-to-person basis, and it doesn't take playing with people you often beat to see yourself doing better. The people around you can tell you that you've improved, and going from constant two-stocks to managing a closer game is a clear indicator, too. Learning should be the most important thing, not winning.
A person who plays competitively and a person who strives to continue to improve are two different things. It's part of what separates the people who don't get out of pools and the people who get into brackets. You shouldn't just be looking for people who just like to play without items; you should be looking for people who want to become better, and have the drive to pursue it, even if it's not that often, or if it's not a main focus, or if they struggle at times (we all do). A person who doesn't care about getting better as a player is not going to continue to go to tournaments, even if he likes the game on a general level. They're not going to be a long-term asset to the community, and you have to remember that spending time with those people will end up with wasted effort after a while, when you could have gotten better yourself with people that are in for the long haul.
It's fine to get new blood into the scene, and it's nice to have people of all skill levels coming to tournaments and playing regularly, but people who aren't committed come and go. I'm not trying to put down the effort of recruiting new players as much as I am saying that the time could be spent in better ways for yourself as a player and for the community if you choose the wrong methods.