The experienced striker scored both goals in a 2-0 victory over Annan Athletic in the League Cup on Saturday.
Having joined the club for the third time in June 2015, the 33-year-old has netted 109 goals for the Rugby Park outfit.
"When you have the finishing ability he has, you can't write a guy like that off," McCulloch told BBC Scotland.
"I've seen it for the last 15 years. Kris Boyd has been written off at every opportunity because he's a bit more high-profile than most."
Ayrshire-born Boyd made his first ever appearance for Killie in May 2001 and is one of the oldest players in McCulloch's squad.
"He's always good in the dressing room, and even when he's not scoring," McCulloch said.
"People like to focus on what he's not doing but I focus on what he is doing. He's always talking and organising on the pitch, which helps me, and he's vocal in the dressing room."
Kilmarnock have taken six points from three matches so far in the League Cup first round and sit joint top of group E, having sustained a 1-0 derby defeat at Ayr United in their opening match of the competition.
"After the first match we knew we had to put a couple of wins together and we've done that," added McCulloch.
"We played slightly different today and it worked for us."
Winger Chris Burke made his second appearance for the club since impressing as a trialist and signing a one-year-deal.
"It's a bright future," Burke, 33, said. "We've got some great young players here at this football club and we've got a nice balance of some experienced players as well.
"We pass the ball well, we move the ball well, we've got combination play, we're scoring goals, we're all comfortable on the ball and it shows the belief that we have in each other."

Work is to be carried out on Edinburgh Airport's main runway over the next three weekends between 23:00 and 05:30.
Areas affected include Bonnyrigg, Loanhead, Fairmilehead, Colinton, Sighthill, South Gyle, Oxgangs, Kirkliston and Bo'ness.
The work will resurface runway areas particularly the touchdown zones.
The airport said 16 flights would operate during the renovations, and the main runway would reopen before 06:00 each morning.
Gordon Dewar, chief executive of Edinburgh Airport, said: "As the airport continues to grow our runway is subjected to heavier loads and more frequent aircraft movements.
"These heavy forces can cause the runway surface to degrade over time.
"The work we're carrying out over the next few weeks will involve resurfacing a number of areas on the runway, particularly at the aircraft touchdown zones.
"As we'll be operating a different take-off and landing route, some areas around Edinburgh may notice a slight increase in the number aircraft operations between the hours of runway maintenance.
"Although this runway maintenance work may cause some minimal inconvenience in the short term, it is essential that we continue to invest in and improve our facilities."
Kilmarnock boss Lee McCulloch believes front man Kris Boyd has been "written off at every opportunity".
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Residents close to Edinburgh Airport have been warned about increased aircraft noise while the regular flight path is temporarily changed.