Thierno Barry scored twice, and Kiernan Dewsbury-Hall added a late third as the hosts recovered after Yann Gboho had put Coventry ahead early in the second half.
Lampard was left frustrated as he felt Coventry should have been awarded a first-half penalty when James Tarkowski pulled Yirenkyi’s hair while challenging for the ball, but referee Stuart Attwell rejected their appeals.
The rules on hair-pulling have been relaxed this season, with officials also considering intent and the degree of force when deciding whether an offence has been committed.
"They're saying it's not enough of a pull, and I think it's a hard area to be in. What is a hair pull? You've decided it is, but it's not enough," Lampard told reporters.
"I think the rules are fine. It's not a red card. I kind of get that because I think in a game of football there's a lot of stuff that happens that's not absolutely dramatic.
"If the rule remains that it's a foul, so I felt it was a foul."
Lampard also said he thought Vitalii Mykolenko had fouled Taiwo Awoniyi near the edge of the penalty area and that Barry had handled the ball before scoring his second goal. Video assistant referee Timothy Wood ruled there had been no handball offence.
"The Barry one is handball. I've heard they are saying it didn't touch his hand, but I've seen an angle where he has flicked it in with the final touch. VAR is there for that," Lampard said.
Moyes: 'I think it's ridiculous'
Everton manager David Moyes, whose side climbed to fifth while Coventry remained 16th, rejected the handball claim but also criticised the hair-pulling rule.
"It certainly doesn't hit his hand," Moyes said. "The hair-pull rule has changed, so it would be a booking if it was, but I still think it's ridiculous that rule is in the game."
