If you just want to learn basic electronics for the sake of curiosity, it's definitely possible to learn things yourself. There are a lot of awesome resources online. If you are interested, I can link you some.
However, if your goal is to be employed in a circuit design or firmware development job, it's probably not realistic. Many people go through a bachelor's degree in EE (which is fairly difficult compared to most other degrees) and still can't find a job. It's something that's extremely hard to self-learn compared to something like programming.
If your goal is to get employed in the electronics design / firmware industry, your best bet is probably to get a bachelor's degree. Since you already have a related degree, I'd guess you can skip a lot of the courses, but there would still be a lot more to learn. It's definitely not easy, but very rewarding if you are actually interested in it (like I am), and there are definitely no shortage of jobs if you are talented. Companies actually FIGHT for talented electrical engineers because they are hard to come by.
