I started playing in Wave 1, but my local scene took a hit around Wave 3. It was more to do with a 2nd game store opening up on the other side of town that split the scene. I quit for about a year and came back right about Wave 4. It was just me and another guy at first. I slowly worked to build up the scene and our local FB group has about 200 people in it. There are now a lot of game stores and there is an X-wing game every night of the week at a different store. I've met a lot of different types of gamers get into the game and I've seen a good number of people leave the game. For my part of the world, I feel like I've got a good pulse of the game and what attracts and repels gamers to it.
If you want to fix the scene, it's one thing. If you want to just grow new players, that's another. I think both are good things to do. It might be easier to fix it for some players and then work hard to bring in new players. A lot of it depends on what types of games people want. I have found it's easier to keep players and bring in new players if you have more of a casual environment. That's not always the case as you do have some areas that love and thrive on the tournament scene. Most people fit somewhere in the middle and having both types of game nights is the best way, though.
Trying to grow the scene has lots of cool and fun things you can do. It usually revolves around doing something that looks really cool. Epic games, trunch runs, or even just missions using old 40k scenery.