because the force prevents them from self injuring with a lightsaber

That's fine, but they keep putting themselves in the range of their opponents' light sabers. If they'd made the lore that a Jedi / Sith can exude a force field that allows them to take a hit with a light saber and that only a certain, powerful type of hit can do damage, then maybe they can be justified in getting within the other's striking range. But, really it's just that they want these extended slash and parry sequences with these light-up devices so they end up with these silly, unrealistic fights that are badly filmed to show the action and instead just show twirling glowy things.