I started playing again about 2 years ago after 10 years off. I think the table time theory is, in some ways, a limiting belief. Table time is important when you are learning and you need some maintenance but I have steadily improved the last two years playing only once a week at leagues. I had a few long sessions after I started back and then some big things came up in life and caused me to limit my time.
You don't need to learn how to play, you need to remember how to play and more importantly, get the killer instinct back.
Shots won't look right. Your position play will be off. English might or might not take like you expect it too. Deflection and swerve will be slightly different and your fundamentals won't be as solid as when you quit.
My strategy has been:
1) Go back to fundamentals. Make sure your stroke is straight. Your stance is good. Your eye position and alignment is where you want it. And that you are the right height above the cue. For me, after 10 years it was difficult to get down as close to the cue as I used to.
2) Once your fundamentals are solid, or at least solid enough to practice without making things worse, work on aiming and ball pocketing. Start with fairly short straight in shots. Just focus on hitting center CB and hitting the OB straight into the center of the pocket. Then get longer until you are shooting full table diagonal shots. Seeing where you are aiming is more important at this point that making the balls. Keep working on this in the beginning of every session. If your fundamentals start to drift it will show up here. If you remember how you used to aim, look for those reference points and fix them in your mind.
Then set up the L corner drill and just take BIH and shoot balls in from different angles. Pay attention to where you are aiming to make the balls.
Soon you will be feeling it.
I found that there were a lot of shots that were 'automatic' in the old days. I had no idea how I was aiming and what I was looking at. Sometimes if I just shoot without thinking those shots go in. But if I do that I miss a lot of other shots. So breaking down aiming felt mechanical and forced. But I'm glad I went through the effort now.
3) Start running out a couple of balls. Set 2-3 balls on the table in easy positions and take ball in hand and run out. If you miss take ball in hand and finish them. Then if you run out, throw an additional ball out for the next one. So if you run 3 out, then throw out 4.
Try to do this only using the vertical axis. Plan your runs to use the vertical axis.
Depending on how well you used to play, if you can work on these super basic fundamentals for several hours or a week you should be making balls and playing position close to where you left off. If you keep incorporating this into your practice regularly you will soon surpass where you left off IMO.
4) Speed control should come back naturally as you are running these balls but if you are struggling then just set up some cut shots and try and make the CB travel set distances after contact. I usually position a ball that I want to gently nudge with the CB. Everybody thinks about speed control differently. I try and move my arm a certain speed. Honestly my speed control came back very quickly.
5) Sidespin, runouts, and clusters - If you were a good player, once you have the fundamentals back on track you'll be ready to start working on sidespin and game situations. I set up straight shots and played them with extreme sidespin. Then worked back from there. Eventually playing an entire rack of balls with inside on every shot. Then an entire rack with outside on every shot. This is where things will start to come together. I still do that if I do manage to get some practice time.
6) Be patient and kind to yourself. This is not the time for negative self-talk or punishing yourself for missing. You should take ball in hand whenever you miss. Have a curiosity about why/how you missed or hooked yourself. Laugh and set it up again. Don't do drills that punish you for missing. The reason I say this is that you are trying to get your confidence back. Trying to get in that flow state. You are trying to explore and remember how you used to play. If you punish yourself for missing then you'll only play things the way you already know how to, the safe way. And that's not what we're after here. The key is explore, experiment and low expectations. Just play. Have fun with it.
I believe that the main reason young kids take to pool more quickly than adults is that they are not afraid of missing and they thoroughly enjoy the whole process of learning and experimenting with pool. As adults we are programmed against failure. Against missing. And that hurts our growth. Not just in pool, but in this case, especially pool.