Keep the outside weather outside without trapping all your own heat inside.
A waterproof shell is most useful when the layers underneath are adjustable. If you start too warm, you can end up damp from the inside even while the jacket is keeping rain out.
Hoods, cuffs and enough room to move tend to matter more in real rain than a long list of marketing numbers you never use.
Wet ground is often the bigger change than wet air.
Grass, stone, roots and stepping stones can behave very differently when wet. That is why footwear and route suitability deserve as much attention as the jacket.
The Chee Dale and waterfall photographs above show the kind of terrain where grip can matter more than whether your outfit looks like proper hiking kit.
Pack wet items so the rest of your bag does not become wet too.
A simple internal bag, dry pouch or separate section for important items can be more useful than buying a highly technical backpack. Protect your phone, spare layer and anything else that needs to stay dry.
If the organiser shortens, moves or cancels the route because of conditions, that is part of sensible event planning rather than a challenge to prove your gear can handle it.