What does writing mean to you? What do you get out of it? Do you intend to keep it as a hobby or do you have hopes and aspirations of something more to come out of it? If you regard writing as something that gives you personal pleasure despite the quality of it, then by all means, go for it, hone your skills and have fun. If you intend to have your writings published and it gives you a positive feeling, despite the quality of it, then by all means, go for it. If you intend to become the next BIG THING of sci-fi or thriller writing, then go for it, the market will take care of that dream of yours, however it may end. Anyway, if you have fun writing the things you want to write about, then write and don't let anybody convince you otherwise.