There’s no one major problem here, I don’t think. It’s a lot of little things that add up. Watch the replay and you’ll see. I miss production cycles, I run from three-cannon wall-offs when I should have just broken through, and I wait way too long to tech past MMM to get a few ghosts in my army. And when I do get ghosts, my EMPs are awful. It also would have been smart to get a few vikings.
Since my army isn’t as large as it should be, since I’m unreasonably afraid of the three pylons guarding my opponent’s base entrance, and since I don’t make good use of non-MMM units, what happens is the Protoss is able to turtle up on two bases, tech to archon/colossi/stalker, and wipe me out with a single, mass-splash-damage-wielding push. This is the worst kind of match to lose.
See the replay with commentary:
Lessons learned:
1. Don’t be quite so afraid of cannons.
2. MMM is good vs. Protoss, but when a game goes on this long, you have to get some higher-tech support.
3. The advantage of sitting on 4 bases against 2 is lost when you don’t keep up with your production cycles.
4. You can’t let Protoss sit and tech up all game. The splash damage from their higher tier units makes even small tier-3 armies incredibly powerful.