I bought a rain cape when I started riding in the 70's. It worked great as long as I wore it under shelter. In the rain on a bike, water would find its way up from under the bike. After a few wet rides, I cleaned it up, rolled it in a pouch and threw it in the trunk of my car.
Next thing I bought was a nice early Gore-Tex rain Jacket. It worked great until it got dirty, then it stopped "breathing". Plus it stained permanently up the spine from rear tire flow. I also took it hiking, where it developed a permanent stain from the leather bottom of my day-pack.
Then I got a very light Descent wind/rain jacket in Bright Yellow ... its been doing its job for almost 30 years.