There is a difference between Shepard's pie and Cottage pie in that Shepard's pie is usually always made with lamb, which we don't eat.  Neither DH nor I like lamb - yuk.  Cottage pie always uses beef, usually leftover roast beef, but it can also be made using browned ground beef.

My DH love this dish because he likes specific veggies mixed together, i.e., peas, carrots and potatoes!

This is a really hearty winter dish around this house, but I do break down occasionally and make it outdoors in the summer, either using my turkey roaster/oven, the covered grill, or our little portable Coleman camping stove if we have the small propane bottles on hand.

https://www.thespruceeats.com/cottage-pie-3051332