You're right, evolution is an ongoing process. Actually we have witnessed speciation events in several organisms; in these species we are witnessing population shifts that give rise to a new species. For example, killer whales are showing a major shift that will likely give rise to a new species down the road; one population uses echolocation quite heavily, predominantly feeding on fish, while the other population hunts mammals like seals and has largely learned to hunt without echo location. These animal largely breed within their own population so it is likely we will see two separate species arise with unique hunting habits. The article below shares several examples of speciation events we are currently witnessing.
https://blogs.scientificamerican.com/science-sushi/evolution-watching-speciation-occur-observations/
With flies in the lab, we can also see major shifts. One study was able to breed out the gene for wings, and the population shifted towards wingless flies. This is an evolutionary change that is observable in real time. Plenty of evolution can be seen right now, but it does take an incredibly long time to monitor the major shifts; for now we can only observe the minor shifts of microevolution.
Flies, similar to jellyfish, haven't drastically changed in millions of years, but that doesn't mean they aren't evolving. It simply means that the pressures they face have not forced them to change their physical form very much. Like a jellyfish, they are well-suited for survival, so they don't need to evolve these drastic physical changes. Some organisms may change drastically over a short time period while others may go unchanged for hundreds of millions of years!
Herpetologists are also studying a lizard that as we speak is making the transition from carnivore to herbivore, which is a huge change because it requires a different dentition and digestion process.
https://steemit.com/science/@herpetologyguy/lizards-show-transition-from-carnivore-to-herbivore
And what about dogs? We impose artificial selection upon them, selecting for specific traits and characteristics, and as a result dogs have drastically changed since their domestication! Change at the hands of some sort of pressure is evolution, even if it's human-guided evolution!