Writing this as a fellow player. I can see several advantages of not releasing everything at one shot.
We can look forward to stages of releases. If all lands were released on Day 1, some players may feel discouraged and overwhelmed by the massive expansions. Also the bigger our game boards are, the more device resources are needed to run the game. Which means, if they speed up the expansions, players on older devices will not be able to play. As it is, I have some neighbours who are unable to visit my farm.
I have fully expanded and have so much room to spare, much much more than I needed. Out of curiosity, are you of space?