The length of time it takes to fill leagues is alarming, and it’s been bad for a long time. Why not take look at retooling the game to help remedy this issue.
First - reduce the number of teams per league from 32 to 24. Structure the leagues (AL and NL) with either two division of six each or three divisions of four each. It would be simple to set playoffs. Four team divisions - top team in each makes playoffs plus top second place team as a wild card. In six team divisions - top two teams make the playoffs.
Second - HBD combined leagues before when leagues collapsed, so there is precedent for combining or reworking leagues. Seek volunteer leagues to test concept, but I am betting you’d have a long line of leagues ready to give it a go.
Third - improve HOF voting and record keeping by adding to awards things like # of seasons player led the league in AVG, HR, RBI, SB, W, SV, SO, ERA, etc. would give people a better sense of exactly how dominant players were.
Finally - increase the financial incentive for owners to renew and return to a league. Maybe offer a $5.00 discount for owners who renew before rollover.