The €75m Germany striker's form has fallen away since the New Year.
And speaking on The Rest Is Football podcast, Shearer said: "I feel as if, just because of his price tag, he's a centre forward and he is going to get a lot of the attraction. He is going to get a lot talked about him.
"I mean there are other players who have been really poor in the league for Newcastle. Dan Burn hasn't been great, Nick Pope hasn't been great he made another error yesterday. (Anthony) Gordon hasn't been great in the league, in the Champions League he's been superb.
"Harvey Barnes has dropped off a little bit but whether you like it or not, centre forward for £70million or £69million, whatever it is, he hasn't done enough. He's a conundrum for Eddie (Howe).
"In forward positions he hasn't got in the box enough, hence he's played Gordon. He's struggled with the physicality and pace of the Premier League, which okay you knew that it might take time to adjust which is why Eddie has put him into midfield.
"But no touches in the box in the last two games, not enough touches, not enough involvement. He's not the only one.
"They can't get through a low block, they can't get through teams that sit, that's their problem."