Why did it take them 7 films to realise that it makes the effects more convincing if the sabers actually cast light on their surroundings?
They do in AOTC… Anakin vs Dooku
That said, the lightsabers looked awesome and better than ever, they felt really physical and had a certain heft to them. Kylo Ren’s unstable beam and low frequency buzz was a really nice touch. I heard that they made them actually spark on set when they hit eachother. The bit when Finn is first using it more as a melee weapon than a sword is superb.