Riker's rise through the ranks was meteoric. He went from Ensign to Commander in a quite short amount of time, due to a string of incidents bolstering his record
To put it in its proper perspective, he & Geordi are the same age, & at Farpoint, Geordi is still only a LT. JG. It's fair to call Riker's rise from ensign to being offered captaincy, in only 7 years, a feat of superstardom. He was a rising star, who 7 months after graduating 8th in his class, went from the Pegasus, to a stretch of "lay-low" time on Betazed, (probably a couple years or so, likely until the classified debacle cooled off) promoted to LT. scored the Potemkin, then within the year, up to LT CDR. following Nervala, which scored him XO on the Hood for 2 or 3 years. That's too few postings & too few years for Pressman's influence to be insignificant, IMHO.
So, I like to think it was more than just cautiousness or assignment cherry picking behind his decision to be XO on the D. There is even some canon to suggest that he had other issues at play (in the ENT episode we dare not mention)
It boils down to the fact that Pressman isn't being figurative or boastful when he claims to have "made" Riker. That recommendation would aid Riker throughout his career, especially as a junior officer. It very likely opened doors for him he otherwise might not have had, like The Hood posting, & maybe even the Potemkin. I bet that glowing recommendation was still on his resume when he applied for the D posting, when it passed by Picard's eyes
Clearly after the Pegasus, Pressman went up the ladder himself, making his name a good one to drop, & it was only then that Riker realized he had risen on the laurels given to him by a corrupt captain, despite however much distinguishing he'd done for him self.
He was ashamed of himself for being something of a fraud commander, which explains why he never came forward about Pressman later on. He knew he had be benefited from it, & though he gritted through that shame as a commander, it was too much for him to consider becoming a captain under that weight, which is actually why it makes sense that ENT's TATV took place
before he accepted the Titan. Troi counselled him through the shame, & he finally overcame it. (Oh noes, I mentioned it)
And that is the story of Riker, as I see it, but I still believe you have an obligation to accept captaincy when they offer it, for the good of the outfit, despite whatever personal crap you got going on