Part of the problem SC2 units are not very balanced and each patch tries to make them "more balanced". SC2 design settled on making unique units at cost of balance.
Roaches in fact are quite overpowered, with very fast regen and quick ranged attack(they move as fast as hydralisks). A versatile and low-cost unit(cheaper than a Hydralisk). And the reason they're so powerful, SCII units of other races in general are more powerful than broodwar units and have less weaknesses.
Broodwar instead has weak, easy dying units that force micro to extend their lifespan. SC2 units always have easy regen/heal/repair and the player just masses them in huge attack groups with minimal micro(their blocking boxes are tiny and pathing is good enough). The rock-paper-scissors from broodwar(which ephasized soft-counter) morphed into hard counters to everything, which lowered the strategic depth to "make whatever kill the majority of enemy unit type"(since its the best cost-effect decision at any point).
SC2 "pro matches" are never decided in micro battles, they're most a competition on who can more effectively spend resources. SC2 micro is laughably unoriginal and tactically irrelevant(resource competition is far more important).
..And the reason SC2 can't have good micro in principle is not the 3D engine overhead, its server latency and lag. Perfect LAN games in broodwar with sub 10ms latency and millisecond reflexes can't exist within central servers hosting hundreds of players.
SC2 is very balanced when you look at the total game across a range of skill levels. Each unit is balanced around costs, attention, utility, requirements, and other units. Ex queens are awesome early game as they hit air, don't take gas or larva, and have high HP, but late game it's all about healing ultralisks plus anti air.
Roaches take a lot of supply, are armored so take more dammage from tanks and can't hit air which is their counter. They are also ranged so they don't share dammage upgrades with lings or ultralisks. Late game players will sacrifice them for more useful units and they need a larger investment in overlords.
PS: If you watch some high level games units generally have their time to shine as part of individual games progression.
Roaches in fact are quite overpowered, with very fast regen and quick ranged attack(they move as fast as hydralisks). A versatile and low-cost unit(cheaper than a Hydralisk). And the reason they're so powerful, SCII units of other races in general are more powerful than broodwar units and have less weaknesses. Broodwar instead has weak, easy dying units that force micro to extend their lifespan. SC2 units always have easy regen/heal/repair and the player just masses them in huge attack groups with minimal micro(their blocking boxes are tiny and pathing is good enough). The rock-paper-scissors from broodwar(which ephasized soft-counter) morphed into hard counters to everything, which lowered the strategic depth to "make whatever kill the majority of enemy unit type"(since its the best cost-effect decision at any point). SC2 "pro matches" are never decided in micro battles, they're most a competition on who can more effectively spend resources. SC2 micro is laughably unoriginal and tactically irrelevant(resource competition is far more important). ..And the reason SC2 can't have good micro in principle is not the 3D engine overhead, its server latency and lag. Perfect LAN games in broodwar with sub 10ms latency and millisecond reflexes can't exist within central servers hosting hundreds of players.