"Had" changes the meaning slightly:
The last time he had stepped into a convenience store was a year ago.
He hasn't stepped into a store between that moment and a year before.
The last time he stepped into a convenience store was a year ago.
He hasn't stepped into a store between now and a year before. This will not be true if he goes through ...
As you’ve written it, I think had is necessary. It reads off without it.
But re-arranging things, it's not needed.
Standing in front of the sliding glass door, sweating, he remembered last year and stepping into a convenience store.
And, now the statement has some suspense to it. \o/!
I’ve had this argument with another writer, who insists that had needs ...
Yes, but it would be highly unrealistic. The reason humor exists is it's a coping mechanism... people make jokes to deal with uncomfortable topics or get through fears. It's not that it detracts from the work... it's that in a real situation, someone is going to try and bring a smile to the room, even if they're in an inappropriate situation. The work ...
In the present context, it's not necessary to include 'had' in the sentence. Using 'had' would indicate the past perfect (pluperfect) tense, which is used for conveying a sequence of events. The simple perfect just conveys that an event occurred in the past. Either is a reasonable reading of your sentence. You can read more about past perfect here.
You can certainly write a story without any intentional humour, but you can never rule out the possibility of your audience finding comedy in something that wasn't intended to be comedic, especially in the age of meme culture. Thanos' snap at the end of Avengers: Infinity War is a very bleak scene, without a shred of humour, and it took three ...
I think you can remove most comedy from a book, but even just keeping a little bit will help a ton. Just skimming through my memory, I can't remember any (fiction) book I've read that did not have at least a little bit of humor.
I definitely would not have a character hanging around just for comic relief in a very serious world. Rather than have a character ...
You need some humor, but no need to overload it
As the other answers have mentioned, it is somewhat pointless to read a book that is all dark and dreary. So, it is important for you to include some humor. However, there is no need to overload with humor, you're not writing a comedy.
What is humor?
Humour or humor is the tendency of experiences to provoke ...