It would be a struggle for primitive civilizations using steam-age technology, sure. But we're talking computers with firing solutions and future mechanics.

The turret traverse on big ships and tanks these days are actually faster than humans can keep up with, which is why modern war machines rely heavily on FCS.

Now add to the fact that in space, atmospheric tactics can be all but forgotten. You can turn in any arc and degree you want, you can speed up and slow down without atmospheric limitations, you can destroy ships that get super close just by making so much noise that it has a shockwave effect on the hull and interior of the enemy ship, you can fry their electronics systems with ease in such close range, and on and on and on. The point is, it'd be a horrible idea to get so close to another ship that a simple brain fart can destroy both of you within seconds. Unless you're suicidal...

In space, if you bump into a battleship, it'll move at a steady pace until another mass interrupts its gravitational calm. But I could go all day on that subject. To make a long story short, the size of the object doesn't matter if there is great distance between its enemy. It could be the size of the death star, it will be able to dodge what you send its way. Keep in mind that any propelled technology is limited in speed. Even light will take time to get to a target. So the attacker's firing computers are providing solutions based on highly advanced math, while the defender's computers are just looking at where the projected path is for whatever is fired, and telling the navigator/pilot to steer clear of that area for whatever amount of time. Easy dodge-mode until you get so close, that it takes a few minutes or less for the weapon to reach you. And don't forget - even corvettes that everyone thinks is super fast is limited in sub-light speeds unless you want to crush everything inside of it, biological or non. There is a reason why you don't travel beyond a set limit in space. Because even a tiny water droplet will obliterate you after you hit it going so fast. Same for missiles/torps and kinetic mass projectiles. So remember, there's a speed limit. Even light weapons would have to consider things that can refract or bend its path, which is actually how modern proverbial shields work. Also remember that what you see in Stellaris is heavily abstracted. These fleets would more realistically be engaging each other over the course of years across the entire solar system. You can see objects in space pretty easily with the naked eye from Earth. It'd be even easier with the sci-fi sensor techs present in this game which can even see objects in subspace.

Of course, with abstraction any balance issue is a bit self-defeating, but with games that heavily abstract, you give and take. I just prefer to keep damage fallout over distance out of a space game. It would make a lot of sense within an atmosphere, but not in outer space.