Particles are visual effects. They should not consume your CPU resources. Unity's built-in particle system runs on the CPU and is therefore very limited in terms of particle count. GPUs, on the other hand, are designed for parallelization and can compute and visualize extremely large amounts of data. That's why I programmed a GPU particle system for Unity that is capable of processing millions of particles per system and providing amazing visual effects. It also comes with a fancy custom editor to quickly change its many parameters.