I wouldn't say For Glory is useless. One thing I feel that it is good for is seeing different playstyles and, even against crappy players, you'll sometimes be surprised by tricks and tactics you never thought of. For example, I think I've learned more tactics with Megaman and Villager on For Glory then I ever did watching matches on Youtube or Twitch. Another thing it is good for is gaining general and practical match up knowledge. For example, you learn what constitutes good and bad strategies for different characters, which moves you shouldn't use a lot (or at all), basic set ups, etc. After awhile, you get a decent idea of what makes a decent
and what makes one you can almost entirely blow off.
I have close to 20,000 matches on it and can also say that not everyone on it is god awful. Like you, some people are pretty isolated and it's one of their few competitive outlets so there are actually a lot of people on there that suffer from "Sandbox Syndrome" (basically being the guy that destroys their friends, crushes locals or has a popular steaming channel but gets flattened at state/national level tournaments). I'm definitely like this because I always run away with locals (only dropping one set this whole year so far) but would probably be crushed if I went to one in a major city (which is extremely rare in my area) so decent players do exist on it. As people have said, if it really bugs you, save your replays and watch them to get an idea of what you're doing wrong or post them on here to show us. Just upload a match where you get BTFO and we can commentate if you want.
Also, I just noticed that you main Wario and Robin and both have pretty steep learning curves so you may want to switch to easier characters to get a better handle of fundamentals first.