Mills said there was no bottom line in it for restaurants and the past few months had been challenging due to a change in government and financial instability.
"The hospitality industry is going through a little bit of a hard time so I think it [WOAP] should be more focused on helping them generate more income rather than working your butt off and all your staff's butts off for very little reward."
Mills said he didn't have a problem with the event being a Burger Festival if organisers were up front about it and called it that.
He suggested Burger Wellington be paired with Beervana leaving Dine Wellington to run separately.
"I think mixing them all into a two week period makes it a little bit complicated and takes vision away from where it should be."
Italian restaurant Monte Cervino owner Sean Marshall also said burgers had taken over the event and were "diluting" Dine Wellington menus.
He said it was disappointing some restaurants didn't get the lift from the event they were hoping for, especially after a tough few months.
"Based on this year, I wouldn't take the risk of not doing a burger next year, it's as simple as that."
La Bella Italia owner Antonio Cacace said WOAP should be more open than just focusing on burgers, which was also limited to chefs' innovation.
"The beginning of Wellington On a Plate was fantastic, they were covering almost everything."
Meat Direct owner Victor Smith said the scene was vibrant this year but agreed burgers had taken over from what the event was all about in the beginning.
"What we try to do is make sure we get a nice balance of products into our restaurants but yes, I've probably sold more mince, different types of mince, whether it's pork, venison or beef. That has been a lot more popular."
He said WOAP had lost direction.
"I certainly wouldn't want to get rid of it but it needs to just get more balance for everybody right across the board
WOAP programme manager Beth Brash dismissed the idea the event had turned into a burger festival.
She said it also offered a cocktail programme, dining options, sell out events including international chef collaborations, and community events.
"The offering that we have across the whole festival is very diverse and there's definitely something for everyone."
Brash said the festival was a constantly evolving "moving feast" and this year's feedback would be taken into account to shape any changes for 2019.
"The festival exists to make Wellington and Wellington hospitality great and if we aren't doing that, then I need to work harder, then we need to work harder as a festival to make it great for everybody involved."
She said it was too early to consider whether Burger Wellington could be separated within the event.
