Your hip flexors have a tendency to become tight since we as modern humans tend to sit a lot. This is turn can lead to glute inhibition which means theyre not activating when they need to. Glute hip bridges, barbell hip thrusts, glute hamstring raises etc are good exercises for training your glutes to work properly. Whenever I stretch my hip flexors my glutes work better because the purpose of the glutes is to keep the hips in a neutral position. If the hip flexors are tight you are literally being pulled forward and can cause lower back pain and a myriad of other problems.