It always seems bizarre to me that people complain about software now. You can just write the thing you want. If you want to do things in parallel do them in parallel. Claude Code will allow you to run multiple instances in the same folder and let them communicate. Previously I used to let them intermediate through a communication bus but now they seem to be able to talk to each other.
I let most agents work asynchronously and don't pay attention so I don't care that much about the sequential nature. But if it's a problem for you then fix your harness. This is a bit like saying "Why are shoes so shit? There's a stone in one and it just gets stuck there and your foot steps on it and it hurts". Take off the shoe, and shake out the rock. Put the shoe back on. You have the power.
I let most agents work asynchronously and don't pay attention so I don't care that much about the sequential nature. But if it's a problem for you then fix your harness. This is a bit like saying "Why are shoes so shit? There's a stone in one and it just gets stuck there and your foot steps on it and it hurts". Take off the shoe, and shake out the rock. Put the shoe back on. You have the power.