I think the reason RE5 really took away any horror elements was due to co-op. Games just aren't as scary when you have buddy next to you or across the interent, and I think that shift alone really directed the game as a whole. It became more about widescreen action set pieces and strategic positioning/gunplay, less about surviving with limited resources or that creeping eerie atmosphere. The idea of "support" really fundamentally goes against Survival Horror, which is probably why they transitioned RE5 wholesale into action territory.
I didn't mind though, RE5 in co-op is probably the best experience I've ever had with the series. It was actually a little hard to go back to RE4 (and it's looooong escort missions) afterward.