It is tempting to suggest that part of the reason for the reaction against Drift is that Drift is not an actual character from the original era of the Transformers franchise, despite his being placed in the nominally Generation One (referred to as "G1" hereafter) stories produced by IDW comics. But Drift is hardly the first "neo-G1" character. The Japanese retailer e-HOBBY had created several such additions to the G1 franchise in the years previous, perhaps most notably Sunstorm, and few, if any, of these have generated the fan-antipathy that Drift has. While it is certainly true that most of the e-HOBBY additions were just repaints of existing G1 molds, I hardly think that Drift's distinctiveness in having been designed more or less from scratch is the source of fan hatred.
I think it's safest to say that the animosity toward Drift arose out of the way Drift was originally promoted and presented to fans. Perhaps the note on Drift's TFWiki page says it best:
...Basically, he's frequently viewed as a stereotypical badass fan-created character with Japanese samurai/ninja stereotypes added in for maximum awesomeness. The main reason given by fans for their criticism, however, is the initial hype the character was given by its creator and IDW, which fans believe created a massive hype backlash.... Many fans think that while Drift's actual fictional appearances aren't nearly as bad as the most vocal critics make him out to be, he certainly fails to live up to the hype. In fact, a lot of former critics feel that the later interpretation of the character by author James Roberts is actually quite decent, redeeming the once stereotypical character somewhat.I'll be honest, I wasn't thrilled with Drift's introduction into the franchise, myself. Basically, I saw him as taking time away from characters I cared more about, while doing little of note to justify why he was used rather than one of these other characters. I was even less enthusiastic about the fact that Drift's existence was to be further rewarded by having an actual toy — called "Autobot Drift" for trademark reasons — made in 2010 (again, why not do a real G1 character that hasn't yet been remade?), and so I didn't pick it up for a long, long time. In fact, I only did get him when he was available at Marshall's for roughly half his original price, and even then I might have passed it up, except that I trusted the online reviews from fans who said that, yes, whatever one feels about the character, the toy is actually pretty nice. It boasts a fairly innovative take on the car-to-robot transformation that has been done so many times in the past 28 years, and the way that the shorter swords sheath into pockets on either of Drift's sides (which nicely resemble scabbards) in robot mode is quite brilliant. Also, the toy has better-than-average articulation (even for a modern-era toy), enabling him to grasp the long sword by both hands at the same time! If you manage to see this toy on the shelf (especially at discount prices!), I recommend looking past any fan disdain you may hold for the character's origins and introductions, and go ahead and pick it up. I really don't think you'll regret it.