You're not wasting your time.
Just remember that the Smith doesn't allow for natural motion.
What I mean by that is you're having to make movements based on what the machine allows rather than your natural movements based on your ROM.
I only use the Smith when I am alone (no spotter) and am going to be lifting to failure or I use it to "test" myself when moving up in weight.
Because I most often work out alone I end up using Hammer Strength a lot more than I should and the Smith when there's really no alternative.
Why are you concerned with a spot ? If you can not control the weight and do strict reps you are lifting to heavy , IF and only IF you need a spot it should be on your last rep or 2 of your last set . If you need somebody to spot you during your whole workout then you do not know how to train . Just being honest with ya , Hope this helps . If you only need a spot on 1 or 2 reps ON YOUR LAST SET then just ask anybody in the gym . Smith machine is nice to throw in the mix but use the dumbbells until you learn how to fully control the weight on your own then move to the barbell . Then you can switch back and forth as need be btween DB and BB once you have some experience in training the correct way . YOU DO NOT NEED A SPOTTER TRUST ME
I hate the range of motion on a smith machine. My gym doesnt have decline bench press and whenever I try that using the smith machine for it I get no chest workout from it. Imo dbells are the way to go, hammer strength, and regular bench. Also, the regular sweeping motiom of a bench press movement imo cant be replicated on the smith machine thus making it not as effective. I use the smith machine to burnt out on shoulder press, calf raises, etc.
I almost never have a spotter, my workout partner is my wife. She spots me sometimes if I really need one but obviously I have to know what im doing. Like others mentioned you should not need a spot on a regular day and still be able to go heavy during your sets.
These days I rarely use any machines. I much prefer free weights and body weight exercises. I want my body to manage and overcome the instability of the big free movements. Much more beneficial to a total synergistic body than isolating body parts.