Worthwhile, interesting subjects usually are. The more you work at it, the more you learn and the more proficient you become. To some level of proficiency, all of us can learn these things. They become easier and more enjoyable as we work at them and achieve skill.
Science is no different.
The more background you already have, the easier the next science course will be. Because you will have encountered the major principles before, less of the course will be new to you. If you have a weak background in science, then some of the principles will be new to you, as well as the special applications. However, all of the course content is accessible to any capable, motivated university junior or senior. The information is presented from the beginning, from first principles, assuming no previous background in the subject.