Too many walks
We dealt with the strikeout problem by moving the pitcher back. We can deal with the walk problem, too, by making walks harder to get.
There are two ways to do this, and since both achieve the same purpose feel free to advocate for whichever you choose.
The first — also the simplest — is to slightly enlarge the MLB strike zone…probably at the top. Pitchers are throwing higher these days anyway, and having moved the mound back to disadvantage the pitcher we need to compensate them in some way.
Moving the top of the zone up to the bottom of the armpit – where, for the record, it was until 1987 – would accomplish the purpose.
But there is another, albeit more revolutionary way. Change the number of balls required for a walk from four to five.
There are disadvantages to this, the most obvious of which is tradition. Batters have gotten a walk after four wide ones since 1889. The other drawback is that this change would, to at least some degree, lengthen MLB games, which is the opposite of what the commissioner and most everybody else is trying to do.
So it may be best to focus on a larger strike zone.