I'm not a fan of banning shifts. Baseball seems intent on turning the game into a HR derby.
The shift actually increases the likelihood that someone will be swinging for the fences.
Here's the logic ... the shift REALLY affects left-handed hitters (LHB). A LHB has a natural advantage against right-handed pitching (RHP) because the ball takes longer to come in to them ... they have an extra moment to decide on their swing, and to get around on the ball. This is why down and in to a LHB is usually death. They're going to rope hard hit balls all day long (comparatively and relatively speaking, of course). Grounders, bounders, line drives and fly balls.
The shift basically takes away this advantage ... and then some. Now, a LHB has 2 choices ... they can either try to hit only OVER the shift (doubles and HRs), or they can try to go opposite field. And the latter option is what all the shift-proponents and oldenheimer small-ball advocates scream ... "Just go the other way ... or bunt! Duh! No more shift!" Except it's not that easy. In fact, it's not really possible. With the shift allowed, a RHP will pound a LHB inside all day. These guys are throwing 93-95 mph (or harder) cutters in on the fists. You simply can't go the opposite way with that ... not with any reliability ... and not without completely changing your swing/approach so that you can't take advantage of other hittable pitches. This is why you see guys still hitting into the shift ... because they're trying to hit OVER it, as the alternative isn't really an alternative at all ... despite the cries of the hitting experts on their couches.
The shift sucks. "True" lefties (left-handed throwing and left-handed hitting) are screwed over in baseball ... they can only play 4 positions (outside of pitching) - 1B and the 3 OF spots. 3 of those spots are traditionally bigger-bodied power-hitting positions. And, lefties, due to their non-shift advantage at the plate, are naturally more power-hitting, regardless. So, you're asking the very few lefties that make their way up into the pros, based on their stroke, to do things they're completely not equipped to do (if they're even possible, at all).
So, you limit a lefty's opportunities by the nature of the game, force them to become a certain type of hitter to make it in the bigs ... then you take away that ability/advantage. What happens? Well, as you could expect .. there are fewer and fewer lefties in pro baseball every year. And with fewer lefty-hitters, there are fewer lefty pitchers needed.
Yes, I know ... you can find exceptions to this ... small lefties who made it, lefties who hit to all fields and rely on speed/contact ... but those are the exceptions.
And the solution to fix this situation is easy ... have fielders play where they traditionally played. Nothing at all drastic. Just go back to the way the game was generally played since its inception. Football limits the offense's advantage by demanding a certain number of players must line up on the line of scrimmage ... baseball can prevent the defense from getting an advantage on hitters.