Thanks for your perspective. Like most of us, I’ve toyed with machine training but never been dedicated to it. I decided to include it today, but more as a finisher.
Example: Today was an upper body session. For GPP, the meat and potatoes of it was a 15 minute density block alternating dips with rope pull-ups for sets of 4 and 3. After the density block I went through some machine exercises, mostly single joint, for 1x20.
I think you could present the argument that some assistance/supplemental machine work (that is thoughtfully programmed for an intermediate+ lifter) may improve your compound lifts and thus improve your perceived performance long term. That being said, if someone comes on here and starts talking about how they nothing but quad extensions, hamstrings curls and Nautilus presses to prepare for their DIY OTC public land hunt and that they "had no problems in the mountains", then they are full of shit.
You could make the case for some lat pull downs if you can't do pullups/chinups.
You can definitely create some additional muscle stretch by manipulating the angles on machines, but, I'm having a difficult time coming up with anything other bicep curls, tricep extensions, pectoral and shoulder exercises for this example. I suppose you could consider cable rows, but its difficult to see how that would benefit performance more than barbell or dumbbell rows (or deadlifts for that matter). I'll throw in a few weeks worth of various tricep extensions on the cable machine every now and then, but I don't anticipate that improving my performance on anything beyond the bench press. Of course, bigg bench press = stronger upper body = ability to support my load on the body = carrying more weight more safely, but, if you're to the point that you need tricep assistance to further drive your bench press, you're already beyond the realm of improving your performance in the mountains.
Machines are good for hypertrophy of isolated muscles, but from a mountain performance standpoint, its "all show and no go" Will it negatively impact you? probably not. Is it better than nothing? yes. Is it the most effective use of your training time and energy if your main goal is mountain performance? unlikely.
Now, some people just want to be jacked and happen to also like to go hunting. If that's you, knock yourself out. I personally am stronger than I need to be to effectively go hunting, but I place some amount of value on being strong and also happen to go hunting. While I'll argue that strength is super beneficial for your long term health and ability to do difficult things, I don't know if there exists a convincing argument that machine based training is the best way to increase your real world performance.