40K is schizoid in it's tech.
The best way to understand it is that the tech itself is quite powerful, but the people using it are hamstrung from getting everything out of it.
Lasrifles are the same fundamental tech as Lance Batteries -- just a question of scale and degree of hyper simplification. If someone were to take the same stance on how to build weapons that we use today, and use that standard to make a lasrifle, the weapon would be far,
far stronger than what most Imperial Guardsmen get ... but it also would require more complex maintenance than a literal shit-smeared peasant banging it with a rock, such as actual tools made for the job and being kept clean.
The easiest comparison here I can think of is Imperial Guardsmen's
Flak Armor, which is standard issue, and the late series armor offerings in Stargate SG-1 to defend against ma'toc staffs. And a lasrifle has semiautomatic mode firing. That's honestly the best comparison I can think of to help calibrate tech potential.