Training your kids to love the outdoors is simply about giving them experiences and opportunities to succeed. Never about forced marches LOL. Well, maybe a little. But the march is only a mile and the forcing is that you won’t carry them on your shoulders for more than half of it.
(Oh man just brought up a memory of my kid when they were 5, they were such a runner!!! So we signed up for a family 5k. Everything was going great until I made a fatal mistake: With less than a mile to go, kid absolutely doing great & happy, not pushing kid too hard or anything, I said “wow we’re almost done, all we have to do is run to the finish line over there” and I pointed and “over there” was to my child IMPOSSIBLY FAR AWAY. Kid made it anyway but was not so happy after that.)
My other parenting tenet is that kids should always be part of the solution, not the problem. Building a healthy family team means that everyone contributes. Basically this means you deputize kids to do certain things (e.g., you’re in charge of sweeping the campsite, you’re in charge of weeding), and delegate age-appropriate responsibilities to them.
Finally there are tons of fun groups that do stuff like this through sports or camping. Consider water sports, sailing, biking, roller skating, go-carting, fort-building, scavenger hunts, orienteering, dog training or sledding…
To boast a bit, we successfully raised some wilderness experts! They are into mountaineering, camping, water sports, sailing, biking, etc. and have led multiple summit climbs.
That said, my kids enjoyed being outside almost from the moment they were born. So who knows if we deserve any credit for the parenting side of it.