The England star did not hold back in his assessment of the club’s performances as they prepared for their critical game against Catalans Dragons.
Giants are one of four clubs locked on 20 points at the foot of the table and know if they lose their last game tonight they could be relegated from Super League.
Owner Ken Davy has spent millions on Huddersfield who won the League Leaders’ Shield in 2013 but, yet again, it has been another dismal campaign.
“We’ve let everyone down: Ken, the staff, the fans and it’s not just the one person,” said McGillvary, as they aimed to finish on a rare high at John Smith’s Stadium.
“As a group of players we haven’t been good enough. It’s one of those things that will need to be addressed and we’ll probably have to have a few players changed around.
“We’re not good enough as a side; the table doesn’t lie or make up stories. We are where we are for a reason.
“We’ve been absolutely shocking this season. A lot of teams would be lucky to have an owner like we do but continually over the last three or four years we’ve just not been good enough.”
Many people see Giants, in 10th, as best-placed to survive given they are at home to injury-hit Catalans Dragons, who have lost their last four games and seen play-off hopes dashed.
But Huddersfield-born McGillvary, 31, warned: “Catalans don’t have anything to play for and have five or six new players in their team but it’s a bit dangerous going in thinking it’s an easy win.
“Some of those coming in are making their debuts and they’ll be looking to impress Steve (McNamara).
“With nothing to play for, they might play a lot different to what we’ve seen or what we’re thinking. But we just need to go out there and be professional. We haven’t done it many times this season but we need to go and put a good performance in.
“We owe it to the fans who are coming to watch. After what we’ve dished up this year that’s why we are where we are.”
McGillvary conceded he has contemplated what life would be like if Huddersfield were relegated again, as they were back in 2001.
“I’m not going to lie,” he said.
“Over the last four or five weeks you have to think about that situation.
“We’ve not been playing well and with what’s been happening at the bottom - other clubs picking up wins here and there - you do realise that if the worst comes to the worst, most of us are pretty much knackered.
“Contracts become null and void, you don’t know if you’ll get another club and - if you do - whether you’ll get the same money. All sorts of things go through your mind.
“But this is my hometown club. I don’t want to play anywhere else. I want to retire here as a one-club man when I get to the end of my deal (in 2022) and I want it to be in Super League.
“We’ve got a huge game on Friday and we have to find one big performance, full of energy and effort to get it done.
“We’ve only done that in bits and bats this year but we must do it against Catalans.”