For the long run, you should focus on functional components, as react team has suggested to use functional components with hooks to manage the state for component.
But that does not mean you should completely ignore class components. The reason is in professional life you may come up with the code base that was written before the introduction of hooks using class components and you are not allowed to refactor it to functional components ( there can be various reasons of not doing that) in that case your knowledge about class components will come in handy.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…