Football needs even more development, both physical and skills-based, than baseball to be prepared for the rigors of the professional game, so the emergence of MiLB vs college football/basketball isn't a player development issue.
College sports (read: college basketball/football) thrived outside of the major cities where pro sports were based, especially outside the northeast where the major cities were located when professional sports initially became popular. Minor league baseball also allowed that sport to thrive outside of major cities, due to the lower cost of running the teams and therefore less attendance needed to make teams viable.
College sports were able to grow larger than MiLB due to their association with colleges and the inherent draw that gave them from folks in those areas. I don't see any reason that college baseball would not have grown at least as successful as MiLB had MiLB not existed and had college baseball become the feeder system to MLB.