I owned a few rain jackets. Please look for these attributes in a good rain jacket.
1. Material has to fully waterproof. There are many waterproof materials. Most should work as needed.
2. It must include a hoodie. I prefer the hoodie to be part of the jacket, but I have had hoodies that snap into place. Ideally a rain jacket always needs a hood, hence I see no reason to remove it.
3. Breathability is huge. There must be vents and a layer under the outer shell to allow ventilation.
4. Super long bottom to sit on. This will keep your butt dry, and it will keep the jacket from falling below the saddle. Once below the saddle the rider will not be able to stand up ( the jacket will be stuck and will restrict motion ). This can be dangerous and cause a fall.
5. Bright colors. You need to be seen in the rain, so get bright colors, stay away from black jackets with reflective strips.
6. Pockets. Lot's of pockets make the jacket more usable.
7. Lightweight. I do not like super light, and small packable jackets ( these are popular now ). I prefer heavier ones with some substance. My last rain jacket was made by Bellweather and lasted about 10 years. Super light jackets will never get close to lasting that long.