Glute imbalance

I have had an issue for quite some time and not making much progress. I’ve been doing lots of glute activation (bridge, swings etc) to wake up my sleepy glutes after back problems and numerous hamstring pulls.

This has worked very well but only for my right glute. In glute bridges, hip thrusts, swings and deadlifts (all bilateral lifts) my right glute does all the work. I find it almost impossible to activate my left glute at all. When i attempt single leg bridges aka cook hip lifts, my pelvis tilts a lot and i cant get the glute to work. I have been having back pain because my left lower back takes up the slack and hyperextends.

I would appreciate any advice on how to correct this as its really holding me back! Is it a core strength issue that leads to tilting and preventing activation? If so what exercises are most likely to help?

Also in an effort to bring up my obliques to help with anterior rotated pelvis i’ve been doing leg lowering/ deadbug exercises. These seem to irritate my lower back. What could be the cause of this? My hip flexors are a good length- they pass thomas test. Are there any other good options to strengthen external obliques to help bring my hips to neutral?

Any info or advice would be much appreciated !!! Thanks.