So that 15% range, 20-40 vents, and 20-40 capacitors doesn't mean anything?
Think of the corollary: if it has burn 8, it's automatically the best capital ship in the game.
You also have to pay 15 more OP for that 15% extra range. 10 more OP for augmented engines, 12 more OP for Hardened Shields, 6 more OP for Front Shield Emitter, 4 more OP for Advanced Turret Gyros, etc. The OP advantage over, say, an Aurora, disappears quite quickly once you take into account the increased cost of capital-class hullmods.
In terms of base stats, it's got 100 more dissipation, 2500 more capacity, 100 more armor, and 1000 more hull integrity than an Aurora. The Aurora has 150 more dissipation, 3000 more capacity, 50 more armor, and 500 less hull integrity than the Apogee. Aside from hull integrity, those are very similar increases in base stats; it's literally just a heavier cruiser. Except, of course, both the Aurora and the Apogee have burn 8 and cost 3 fuel/ly while the Cronus has burn 7 and costs 10 fuel/ly. Compare those increases to the jump you get from the Aurora to the Paragon; 400 more dissipation, 10,000 capacity, 600 more armor, 10,000 more hull integrity. Sure, you've stuck High Maintenance on the Paragon, doubling its maintenance cost but not its deployment cost, but even if you halve those numbers it's still more of an increase.
And when you say 15% increased range, are you comparing the Cronus to the Aurora, or the Apogee? Because the Aurora can't even mount a large energy weapon; its range is crippled to begin with. The Apogee can, and I'm pretty sure the +30% range from sensor drones gives it longer range than the Cronus. So when compared to the cruiser that has the most similar weapons loadout, the Cronus probably has
less range.
Even with burn 8, it'll still be held back by having the combat performance of a particularly heavy cruiser. It'll still struggle to directly defeat other capital ships, aside from an Astral stripped of its escort. It will never have the kind of brute killing power and tankiness that a Paragon or an Onslaught brings to the field. It may be the most logistically efficient capital ship, but it won't be replacing the heavies anytime soon.