Considering how differently the Arrow team handled Olicity in Season 4 compared to previous seasons, Marc Guggeenheim’s reveal to EW that he has second thoughts about the pacing of their relationship makes sense.
The Oliver/Felicity relationship became an important part of Arrow back at the end of Season 2, when Oliver made a declaration of love to Felicity that was only kinda sorta maybe a ruse to capture Slade Wilson.
Then, the relationship hit warp speed in Season 4, and it came to a pretty ugly ending before the season was done.
The show played Felicity as the love interest from that point forward, even going so far in Season 3 as to have Oliver remember their one and only kiss when his life was flashing before his eyes.