4 Class Classification - Machine Learning Model
Yes, binning a continuous variable so that in can take discrete values is reasonable, as long as you are OK with transforming this regression problem into a classification one.

Just note that when dealing with a balanced 4-class classification problem, if an algorithm hadn't learnt anything and was predicting randomly it would achieve a 25% accuracy. Your results indicate that the algorithms are at least learning something. It might just be a very difficult task to solve, in that the features might have little to no correlation with the output variable.

I'd suggest trying out more algorithms with and without GA.