Interested what platform are you playing on @Rugbygamer40 ? Im not sure if different platforms effect the possesion or not.
But on PC for me it feels like you have to go out of your way for the AI to take possession off you.
Put up a video yesterday, and I kept New Zealand to 3% possession up to like 30 minutes into the match on hardest as Portugal. And that only changed later in the match because I wanted to test other things and handed possession back over.
The rucks are just about pure speed, as soon as you are tackled just button mash B (if you are using xbox controller) as fast as possible, and dont stop mashing until you pass the ball out. Litterally dont need to push any other button, the jackal and steal buttons seem to be less effective than pressing B, 15 times in a row. Dont let players get isolated. No point using the hold ball function, it just isnt needed.
And if you are struggling go get the ball off the AI, make 2 or 3 tackles in a row and dont commit any players in to the rucks. The AI will always commit 5, and you just wait for them to make the pass to a player thats isolated, then you spam B on that 1 tackle and normally take it. Has dropped from 100% success down to about 70%.
You can even let the AI have a like break, then tackle with your fullback. Your team always beat the AI to that ruck and get a turnover at the expense of losing a few meters.
Also believe team rating difference has a big impact, so if you play with like a 20 rating difference, it will probably be more difficult to regain possession, but thats mainly down to winning the ruck doesnt follow logic, its more of a speed vs player stats thing, and as the lower team you will be worse at every ruck, because theres no other system in place to counter it, like a momentum system, or fatigue from subbed players making them better than players that have been on the field for 75 mins.