The top bar is ranked by popularity, not by merit.
No other automatic system exists to rank boards by merit. Indeed, even an AI could not rank boards by merit because merit is in the eye of the beholder. Thus, the top bar is an accurate reflection of the boards 8chan finds valuable, not the boards specific posters on 8chan find valuable.
You might think to yourself, "but my board is special! It deserves a rank, the system must be broken because I do not have a place in it!"
The system isn't broken, and your board isn't broken. Everything is exactly as it should be. Your board isn't popular and therefore isn't in the top bar.
If you can't be assed to advertise and you can't be assed to see if other board owners will link to your board, no one can be assed to post on your board.
And no, you can't pay for a spot in the top bar. No one donated but if they do they will be refunded.