How do you gain experience when companies are not hiring you to actually get that experience? Will online courses boost my employability?

I guess online courses are one avenue to boost employability, but with so many people taking that route nowadays, I would suggest starting a personal project applying the knowledge you gained from that course. Showcases practical reflections and gives the companies an idea of the kind of work you are capable of producing

Simplest I find is to volunteer and get yourself involved with community activities. From there you can get a tonne of valuable experience, connections and references. You also get to meet and get used to interacting with people that'll consequently boost your interviewing skills - especially when you have a lot of sutff to brag about!