I've been a huge fan of the series for many years, and that's largely down to the ability to create my own game universe.
I've never followed the MLB, or even baseball, so I don't have much interest in playing a modern MLB game.
I'm a football(soccer) fan, and I got into playing this type of game with Football Manager, back in the days when it was still called Championship Manager. As soon as I came across OOTP and realized how much I could customize it, I've been hooked. I've barely looked at Football Manager since.
For me, this is what a true simulation should be. A big sandbox that lets the user experiment with different setups, and play the game as they want.
I never set up any two games using the same configuration. I love that I can make my own countries (Scotland, Northern Ireland, and Hungary) the centre of the baseball world, and with finances and attendances that are appropriate for these countries. No 254 million dollar contracts in my universe

I love that I can play a game with several competing major leagues, or with none, just a loose collection of independent and international leagues.
And I love that I can create a big universe that runs well on my modern-ish PC, but also create a much smaller game that runs well on my hugely outdated laptop.
For me, this game would be so much poorer if it had just been a MLB simulator.