I think that I actually got worse as I got older but I really think it is because I don't play nearly as often as I did 10-15 years ago.
Just stick with it and set small goals for yourself. Don't put too much pressure on yourself to get a new high score but instead try to pick a personal goal for yourself like getting to a certain mode in a game, or completing a certain mode or score X number of jackpots during multiball, etc. It will help you be more consistent with certain skills.
I remember playing pinball with a friend and co-worker many years ago and watching him not flip and instead letting the ball hit the lowered flipper and bounce over to the other one. At the time I said "man I don't have the confidence to do that" and he said "you will, give it time" fast forward a few months or so later after a lot of practice and he was 100 percent right, it was a skill I learned and now has become second nature to me.
6 months is nothing, you have years of practice and hopefully fun ahead of you. Pinball is a skill anyone can learn and get better at, it just takes practice, and lots of it.
I can't emphasize enough the not putting pressure on yourself as it will likely make you play worse. I used to get stressed out and put pressure on myself to play well and win in our pinball league and it would just end up making me mad and want to quit playing. Once I stopped caring about how well I played and just viewed playing in league as a fun social activity where I can spend time with friends and happen to play some games I started playing better at league for the most part and enjoyed it way more, even if I was losing. There has been times that I've lost almost every game of a particular session but I still had fun because in my mind I'm just playing games with my friends and if I happened to win then that was just a nice bonus.
Also playing in a league with players better than you will help you improve as you see things they do that you can try for yourself. I have seen it happen with players in our league who were pretty new to the sport and after a couple years in the league their playing got way better from when they first joined.