The game is widely considered to be well-balanced, which is in part why the game has prospered on a professional level for so long. From what you've listed, Vultures are the only problematic unit (they're the most cost-efficient unit in the game and it plays an important role in every matchup).
If you're curious: Turrets struggle against small units due to their attack type, leaving Terran highly vulnerable against small, mobile Mutalisks in the mid-game. Siege tanks are gas-intensive and immobile in siege mode. Flying buildings' advantage is negligible (Zerg have flying supply depots for that matter). Medics play a very limited role in competitive play: Medic/Marine is sub-optimal against Protoss and Terran, and lately we've found that it doesn't scale well late-game against Zerg too (I find it fascinating that the meta changes dramatically even to this day)! Their blind skill has been used in professional play maybe twice in 15 years. I assume you mean Science Vessels, not Ghosts, can EMP - SVs are gas-intensive, slow, and squishy, but unfortunately are Terran's only effective high-tech unit (Ghosts are expensive and difficult to use well, Battlecruisers are expensive and slow and only see limited use in mirror matchups).
On the other hand, SC2 has struggled with balance issues (perhaps still does? I don't follow it any longer). Anyway the point of this isn't to call you out on lack of BW knowledge (very few people like me care about these details anyway), but I wanted to point out potential confirmation bias: SC2 appearing to nerf or remove these problematic units is not an indication that they are problems in Brood War. Merely a coincidence, if I had to guess! :)
True. At the professional level it is balanced, but at lower skill levels it becomes really hard to counter a terran. Especially the spider mine/turret/tank advancing cycle.
Mutalisks can be countered with Science vessels's irradiate ability since they're low HP.
Sorry, got confused since EMP got moved from Science Vessel to Ghost in SC 2.
If you're curious: Turrets struggle against small units due to their attack type, leaving Terran highly vulnerable against small, mobile Mutalisks in the mid-game. Siege tanks are gas-intensive and immobile in siege mode. Flying buildings' advantage is negligible (Zerg have flying supply depots for that matter). Medics play a very limited role in competitive play: Medic/Marine is sub-optimal against Protoss and Terran, and lately we've found that it doesn't scale well late-game against Zerg too (I find it fascinating that the meta changes dramatically even to this day)! Their blind skill has been used in professional play maybe twice in 15 years. I assume you mean Science Vessels, not Ghosts, can EMP - SVs are gas-intensive, slow, and squishy, but unfortunately are Terran's only effective high-tech unit (Ghosts are expensive and difficult to use well, Battlecruisers are expensive and slow and only see limited use in mirror matchups).
On the other hand, SC2 has struggled with balance issues (perhaps still does? I don't follow it any longer). Anyway the point of this isn't to call you out on lack of BW knowledge (very few people like me care about these details anyway), but I wanted to point out potential confirmation bias: SC2 appearing to nerf or remove these problematic units is not an indication that they are problems in Brood War. Merely a coincidence, if I had to guess! :)