I am using a Canon 70D, has built in wifi connectivity, crop sensor, good at low light levels and a flip out screen which is handy when you have to position the camera in a way that normally would be difficult to use a fixed rear screen or viewfinder. The wifi can be used to connect to a mobile as a slave viewfinder with remote control of the camera and direct upload to the cloud. Video recording is good too.
My Canon 5D is like myself semi-retired now. I do use my wee handy Samsung compact For candid shots and local wild life. My phone has an excellent camera set up too. tbh the phone's camera is the one most often used, my wee grand daughter enjoys the squirrel videos I send her mum on wassapp
I second the 7D mk II or Nikon D500. These bodies have similar autofocus systems, build quality, and ergonomics as the 5D series and other flagship models, but the extra magnification as a result of the crop sensor means you can potentially carry a smaller lens. Both of those models were designed with wildlife photography in mind and also fill our needs nicely. I currently use a 5D Mark IV but was shooting weddings for a bit and needed a full frame.
Keep your old body, always useful to be able to stash a remote camera on an intervalometer somewhere.