Therapy is not a done and dusted issue, it is a lifelong issue I have found post double hip replacement.
I too had a nasty weak leg my left after my second hip replacement, took myself back to physio and found although all my other muscles were really strong, had been doing 3 times a week treading water in the local heated pool, for an hour, then normal housework, shopping, etc my leg was just not right.
Physio took me through sit up's, planks, bridges, which I all did very well I was told for a 65 year old lady, actually she was surprised at how strong I was in some muscles, and then she discovered the weak muscle, gluteus mininus, if I remember correctly, there was an exercise I just could not do, nonsense she said, I want you to try, I did, and she said good news, I can feel the muscle trying to work or twitching, she then taught me to feel for the muscle working, she also taught me about core muscles, although working could always be stronger, within about 3 weeks my walking improved.
I notice you had the same as me, worn out ball and socket, what was left of my ball joint had drilled a hole, on my right side, I had been in agony for a long time, and local GP as I found out afterwards had not dealt with my issues correctly, specialist ortheopedic surgeron when he saw me was horrified, or was well on the way to drilling a hole through my pelvis, when I went into surgery they told me they may have to do a bone graft to fix it, and warned me about where the bone graft was coming from, the back of my pelvis, would be potentially more sore than the hip replacement, thank goodness the cup they put in your pelvis was big enough and with bone cement problem solved.