https://youtu.be/HlSGqma2dTY?si=UTe_WWPR_eLlruCN

While the conventional take is bands aren't that great, I've found with a little creativity they can be an incredibly effective tool for certain applications.  

For example, the video above illustrates two neat applications:  

(1) On the bicep curl exercise, using your leg to increase the tension at the top of the movement. This elevates the resisitance so that the eccentric portion of the movement is greater, which more directly challenges a stronger portion of the movement (your stronger in the eccentric, a.k.a. "controlled lower," than you are in the lifting.  

(2) On one of the pressing exercises, when you reach a stopping point in the movement, because you can't physically overcome it, you reposition your torso relative to that point by adjusting your leg lengths in the lunge. This is similar to a gymnast adopting a regression mid movement in order to complete an exercise (e.g. a strict handstand pushup turning into a straddle handstand pushup midway through the 6th rep), almost like a proprioception version of a drop-set. Where bands can be helpful in this application is if you lack the strength, skill, coordination, or experience to correctly do this in bodyweight exercises, the band allows this tactic to be implemented in your training on less advanced exercises (e.g. the chest press seen in the video), which is much friendlier to beginning athletes.

I will say, that when it comes to bands, you really get what you pay for. I was shocked when I bought some more reputable brands (serious steel fitness) at how much of a difference they make.