Why Lightsabers are a Bad Weapon
I know they look cool and are fun to imagine but the truth is that the Lightsaber is a terrible weapon. It has a number of problems any one of which would make it far less useful than an average weapon. To examine it fairly I am willing to accept the advantages that using it in combination with the force gives, such as the ability to throw and return the weapon and of course reflecting weapons fire. On the other hand advantages of the force are advantages whether you have a Lightsaber or not so are irrelevant to the conversation.
Let's start with the most obvious problem of the lightsaber. There is a reason that people don't use swords as their primary weapon in modern combat. You can kill someone with a sword but you have to get near them to do that. Even assuming that you can get there safely you have still given the enemy the time it took you to travel that distance to do whatever they wanted, including shooting the clone troopers that weren't within swords length of you. It also has little or no value when fighting anything that you can't get within swords distance of such as planes or any reasonably mobile land vehicle.
The argument against this is that you could deflect the enemy weapons and use that to augment your range. This helps some but it doesn't solve the problem. First, you can only deflect weapons which are aimed at you. If the enemy simply doesn't shoot at you it's of no value. Secondly it is only useful against weapons which you can deflect in this manner. That is to say blaster shots. If you were to fight an enemy that used something as advanced as rocks it would be unable to give you any range advantage. On the other end if they were to use torpedoes or other anything that simply exploded when struck it would be useless.
Of course the primary advantage of the lightsaber isn't offensive. It is defensive. The Jedi aren't really supposed to kill people. And in that case it makes some sense. And to be fair there is little evidence that any other defense in the star wars universe is particularly effective at doing this though since the empire puts its troops in armor it stands to reason that armor should have value. In addition we have seen shields that are small enough to fit on a droid so it should be possible to outfit people with at least reasonably good armor or shields in the numbers that the Jedi need.
But the real problem is that the Lightsaber isn't all that good at defense in any universe where people are putting effort into actually defeating it. The problem is very basic. The Lightsaber can only be in one place at a time. No matter how good your Jedi reflexes are you're at best limited to blocking blaster shots in a single line. So in order to kill a Jedi you simply need a weapon that should be very easy to build. You simply make a shotgun. As previously discussed the range of the lightsaber means they have to get into your range in order to attack at which point the shotgun completely negates any defensive ability of the lightsaber.
Want something with a bit more range, or that uses more typical star wars technology you could simply make a weapon that shot three blaster shots in a triangle a bit wider than a lightsaber. A Jedi could block two of them but the third one would get through. And while you might argue that a Jedi could simply avoid that weapon that attack with use of the force that has nothing to do with the Lightsaber.
The final weakness of the Lightsaber is far less important but it is worth pointing out. That is that Lightsabers are very difficult to make. You need crystals that are very rare and the force in order to use them. If it was an effective weapon this might be worth the effort but for a weapon that has significant disadvantages the amount of effort to make it simply doesn't make much sense as a weapon.
Of course there is a final point that the point of the lightsaber isn't to be an effective weapon it never has been. The Lightsaber is a symbol and as a symbol of a group that is supposed to enforce peace and not war having a weapon that isn't good at offense, is only defensive against small groups of reasonably unprepared enemies and that requires a lot of skill and effort to makes far more sense than a weapon that is actually a good weapon.