I used them exclusivly for about a year. Didn’t see any drop in performance. Maybe it isn’t ideal but i’m sure it isn’t that much of an issue unless you are really competing at a high level. Remember you can always do bodyweight exercises as well and plyos etc.
Yes the gurus of the world have slagged of machines for 2 decades and most of them only say-so becuase everyone else says so. I actually think the slanted smith machine is quite good. (used to hate it, have since come to like it. Have only used it seldomly though, and it’s better than the straight vertical smith machine. Feels weird at first.)
They bang on about how machines don’t let you use your “natural” plane of movement. Well niether do barbells. That’s why we look like gorillas standing on hind legs when we go heavy in parallel squats.
Yes all of the above, plus leg extension, flexion, AD and ABduction (occasionally). Remember if you were somehow banned from using free weights you could always use things like slow eccentric glute ham raises etc for the hamstrings as well.
Some of the Keiser pneumatic machines are fantastic, especially Leg-Extension/Hammy Curl. The Hip machine is great too. Most physical therapists have a few of them in their rehab clinics, so if you have a friend in that medical field you might prevail upon him/her to do some sessions.
If you can’t squat to engage the glutes, make sure you incorporate some extensive hill sprints (at least 300m) during the GPP phase (esp if you are a 400m runner). They will light up the glutes, hip bigtime. But don’t go steeper than 15-degrees otherwise you’ll end up using mostly quads to drive uphill, which is OK but not for glute-hams.
You can also do things like two-foot bunny hops, duck walks, monkey hops (bum toward the floor, head up), lunge-walks etc these are massive on the entire pelvic girdle and will (like running) develop all the muscles you need to do the job in sprints.
They all supplement and complement any sort of weights, free or machine.