I don't think Hive Time has quite managed a million players just yet! It's on track for 100,000 downloads this year, I reckon :D
The event that triggers when the last surviving Queen dies has an "I'm having fun" option that allows you to continue playing (unless you enable the "Unforgiving game over" find-your-own-fun setting when starting a new game). It was important to me that the game didn't have any failure points, and that goals and constraints be something that players embraced or rejected based on their own interests and enjoyment. The Jelly goal also serves as a comfortable stopping point for players who aren't enjoying playing for the sake of playing, and a gateway to starting a fresh hive with all their existing research and knowledge for those who are - in my mind, that's where the true game starts.
The playspace is 2,000 cells big, minus whatever obstacles eat up. You can leave hundreds of non-upgraded cells in place and still have room to expand and build many times more upgraded cells without demolishing anything. Staying small (whether that's staying under 150 cells or staying under 75 bees) is a valid way to play and a fun way to explore some of the simulation's boundaries, but that's not intended to be a constraint.
If you skipped the tutorial and didn't review anything in the in-game Beepedia, I'm curious to know how long into your first Queen's lifespan it took you to internalise the "three bees per cell" rule that limits infrastructure use. Even though tester feedback led me to put the tutorial in (it gives guidance up to the spawning of the first Queen), my hope was that all of the game's mechanics and systems would be organically discoverable for an observant player. Each Exit cell in particular has three indicators to show how many bees are currently using it, but many players don't spot that. As a fallback, the info pop-ups for Exit cells covers it, the Beepedia surfaces it in a number of places, and the Activity screen I mentioned earlier also notes that too few Exits limits how many bees can gather resources at once (which again, can be an interesting self-driven constraint, but is not a limitation the game itself is imposing).
If you're interested in where I would have gone with future post-release development, there's a "tentative roadmap" here. It's missing a few things that I had in mind, but didn't want to set expectations for (like alt upgrades for each cell type and role advisor attachments for the Throne), but I think it gives an idea of the broad strokes that I was aiming for longer term. That said, while it has its share of rough edges as all games do, Hive Time is the game I intended to make, and I don't feel like any of the stuff on that roadmap is specifically missing.
I usually do a little patch once or twice a year in celebration of the game's birthday and World Bee Day, but in order to pay bills, my attention is elsewhere and no larger scale Hive Time development is planned at this time. As I said though, if I come up with a way of indicating currently-unlocked upgrade patterns when building cells that would scale to show multiple patterns in a clear way, I'll definitely add it in one of those smaller patches. In the meantime, costs and layouts of already-researched upgraded cells can be seen in the Beepedia.
Thanks again for your kind words. I'm glad to know that you did enjoy the game in a broad sense, and again, I'm sorry to hear that your experience felt more restrictive than what I was aiming for.