Yeah, for vertical, forget about machine exercises. Explosiveness and absolute strength needed for good vertical are built with free weight (barbell/dumbbell) exercises like clean and jerk, power cleans, squats etc.
Machine exercises are best for initial strengthening, muscle endurance and rehabilitation after injuries.
Leg Press is a huge waste of time... I wish they would just remove those gyms.
Like the others have said, it will help you, but you have to use the right exercises, and train in a specific way (low reps always, a mixture of low and high weight, and max effort).
I wouldn't really say any exercise is a waste of time, but if you're doing only leg press for quads then you're definitely not going to get the results you want. Doing leg press after squats is probably the best way to go.
Low reps meaning year 5 or 6 reps max per set. I can't give you the ratio in terms of how sets many to do with really heavy weight and how many to do with fairly light weight, but incorporating both lead to better games than doing heavy weight ALL of the time. The goal is try and power up whatever weight is on your shoulders. Look at Olympic Lifters training regimens tho (talk about training for explosion) they work out based on their previous Max attempt with percentages and sometimes they only do up to 60% of their max in a day. There is a science to all of this but I just don't know all the numbers exactly. Just switch it up between light and heavy... but do mostly heavy. like every 4th time do lighter weight. Something like that.
And Yea with Plyos... really less is more. Like Aussie said, very few reps, very few sets, and massive rest in between. When you get done with Plyo workout you should feel like you can jump as you possibly can on that day... not be tired to jump high anymore. IMO they are hardly necessary if you are doing it for basketball because basketball is plyometrics unless you only play once a week or every couple weeks... but if you play a lot, adding more plyos is just going to strain your body really.