Olicity (as in, the pairing by itself) is hardly the problem. Let's be honest here, this series’ weakest link has always been relationship drama, specially the romantic variety.
I’ve been re-watching the first seasons of Arrow and frankly, I could swear Felicity's egocentric, poorly-justified decisions are exactly how the writers would have written had she continued as the love interest, basically because that how she was written during S1 and S2, (plus a bit of Thea’s bratty, all-about-me behaviour), there’s a reason for Laurel to be the most hated character back then, and for Thea not to be particularly well-liked.
In fact, I could argue that the very reason the Olicity pairing got attention in the first place was because Felicity herself provided a place of levity for the show and looked like a love interest who, as opposed to Helena, Laurel, Sara or even McKenna, could work without degeneration into a drama-focused mess, which is exactly what’s happened.
The thing is, back then the drama problems were a bit more justified, but not because the writers put real effort into making these characters look sympathetic – They didn’t, and the writers got relatively “lucky” that the circumstances their players found themselves in were considerably harder and thus you could understand some of their more egoistical decisions (in S1, every main character had spend five hellish years, not just Ollie and S2, the Undertaking had just taken place, leaving most characters justifiably broken).
The problem as I see it is that, by putting Olicity into the focus, they keep writing themselves into a corner. On the one hand, they want the portion of the fanbase that likes this pairing to feel like there’s time given to them, screentime that appeals to their tastes and favourite couple. That’s fine frankly, that’s just super because they’re also part of the base who watches like the rest, but the first two seasons proved that Felicity and Oliver could work as a couple, so watching them interact should be problem, at least, not bigger problem than having him interact with any other character he loves. On the other hand, they want to have romance-based dramafor some reason (as opposed to, say, other forms of drama, like plot-based, friend-based or enemy-based), I guess because this is the CW, and this is where things just spiral out of control.
Because they don’t know how to write relationship drama. They just don’t. It’s been four seasons and, in one way or another, it’s been almost invariably the most criticised aspect of the season.
Thus Olicity, instead of an aspect that could enrich the series and its characters, became their "get-away-from-jail" free card. Now they could write about all the relationship drama they wanted, independently on whether it was good for the series or not, on how it was reviewed, because they'd have a portion of the fanbase that would constantly support them.
Pandering to the tumblr fans doesn’t mean breaking Olicity up, means putting their love life into their forefront – And making things like plot and characterization revolve around it to a disproportionate degree, at the expense of screen time that could be used for other characters and/or more detailed, engaging plots. And feeling the need to put it into the forefront, they put into the forefront what’s generally accepted to be the weakest of their abilities.
I remember a review, back when it was Arrow Season 2, that called Arrow the best comic-book show since JLU, talking about things that series like Agents of S.H.I.E.L.D. could learn from it. And the biggest thing they could learn from it is that it put effort into cultivating a rich cast of characters with individual, equality important storylines that still fed into interesting, focused stories. This balance is very difficult to attain when you're seeking it, almost impossible if you're more centered into what's, at best, an objectively derivative, repetitive (secrets! lies! will-they-end-up-together?!) and subjectiely unengaging, romance.
.
Being serious. BTW this is not my POV; I figure plenty of people can watch and love Arrow and not love Olicity.
