The Broncos suffered their 18th consecutive loss of the campaign earlier today with a 24-42 defeat against Widnes Vikings.
Three tries in the final 10 minutes gave the visitors some hope at Twickenham Stoop, but the comeback came too late.
"We do tend to come back, but it's not a question of fighting back too late," Grima is quoted as saying by Sky Sports News. "It's a question of playing for 80 minutes, and again we were unable to do that.
"Combined with 12 or 13 errors, we're a long way off our first win after today's performance. It's disappointing as it wasn't through brilliance on their part, just basic skill on ours, fundamental under-six level stuff, which is very frustrating as a coach."
Broncos remain rooted to the foot of the Super League table having failed to register a single point.