There's a 90% chance that almost all of your weight training revolves around sagittal plane or "forward and backward" movements. These comprise all the popular and important lifts you see in the gym.
There's absolutely nothing wrong with this, and I'm not here to bash deadlifts, squats, rows, or press patterns. But while focusing on this plane of movement may be great for muscular development and even strength, it leaves muscles responsible for adduction, abduction, or even rotation hanging out to dry.
That may not sound like a huge deal, but their dormancy over the long haul can lead to serious imbalances, chronic pain, and injury. What you need to do is use small tools to escape the sagittal plane and force the muscles to stabilize load when force is applied in a different direction.
Let's start with the medial glutes. It's surprisingly difficult to maintain a single-leg bridge when the lever arm moves farther away from the body (as seen in the video). Focusing on slow, controlled reps and a maintained contraction on the grounded leg will make the medial glutes work hard to maintain a straight-forward orientation of the pelvis.
If your hips sink or twist (and they will if you're new to this movement), it's a strong indicator that you have some work to do. This isn't the same as doing a squat with a band around the knees. In fact, this is much more effective due to the supine positioning and single-leg emphasis.
Building the glute medius will positively affect the performance of your squats, deadlifts, and lunges, and also act to take stress off of your lower back and sacroiliac region.
As a bonus, the farther you can pivot your raised leg, the more that will speak to your level of active hip mobility, which can doubly serve someone who's tight.