It was probably a mistake to even mention Riker getting his own command. By doing so they put the question out there and unless Frakes quit the show, there was little chance of it happening. It made Riker look weak and stupid when he kept turning down those offers.
Riker did come across as weak and pathetic. He mentioned so many times how he wanted to command a ship of his own. He didn't follow through, though. He talked the talk but didn't walk the walk. It made him seem weak.
Shelby summed it up best.
Shelby to Riker, to his face: "All you know how to do is play it safe. I suppose that's why someone like you sits in the shadow of a great man for as long as you have, passing up one command after another...
If you can't make the big decisions, Commander, I suggest you make room for someone who can."
I loved that scene. Shelby spoke the truth about Riker.
I was surprised that the writers wrote that dialogue into the show. The writers didn't do any favors for the Riker character. They created Riker that way he was, and they went on to tear him down.
Perhaps, Riker's brashness and bravado was a cover for his weakness and insecurity. Whatever the case, Riker's image was damaged by his constant passing over of command opportunities.
By the way, didn't Starfleet command have the power to move personnel around as they see fit? Didn't Starfleet have the power to reassign Riker to a different ship or to a desk job if they thought that was best, or to force Riker to retire for his intransigence in not accepting any promotion that was offered to him?