Ebron has a rep for poor hands. Some WR/TEs just have cinder blocks/frying pans surgically attached to their wrists, NYG RB Andre Williams would be a RB example (Ebron makes spectacular one-handed catches at times, so his drops appear to be more of the concentration lapse variety - a drop is a drop, but this type may be more amenable to improvement if concentration does?). In other cases, there may be variance over time, where they aren't bad for their entire career, but maybe bad in the beginning, middle, end of their career (or even interspersed). If at the beginning, that could increase the chance of a lag, where consensus recognition trails behind actual improvement.
In 2015 (referring to below chart)
http://www.sportingcharts.com/nfl/stats/drops/2015/
Ebron was one of 14 WR/TEs with 5 drops, including OBJ, Dez Bryant, Allen Robinson, Michael Floyd and Jarvis Landry (20 had 6 or more - Julio Jones, Tyler Eifert and Randall Cobb had 6, Julius Thomas had 7, Michael Crabtree had 8, Demaryius Thomas and Martavis Bryant had 9, Brandon Marshall and Amari Cooper had 10 and Mike Evans 11). The list is sequenced by drops. The last column shows drop PERCENTAGE. Ebron's was 7.1%. Notable WR/TEs that were worse included Evans (7.4%), Cooper (7.4%), fellow TEs Eifert (8.1%) and Thomas (8.8%), as well as Bryant (9.8%).