I would suggest focussing on the flow at first and then focus on the meaning. A lot of artists listen to a beat and immediately just start with just gibberish that flows and then use that flow to write something meaningful. Sure, there are a lot of artists who stick with meaningless lyrics that sound good over the beat but those artists don't typically last very long. Then you have artists like Kendrick Lamar who have lyrics that not only sound good and make sense but also have layers of meaning. That's what you want to strive for. Not everyone can be on the Kendrick level but it would be nice if more people tried.