I have a stupid theory:
The main playable character (aka the player) is actually NOT Commander Keen/Billy Blaze!
Let me explain...
See, on the timeline Commander Keen series are situated somewhere in the early 90s. Billy Blaze was born somewhere in the early 80s, growing up, living his life etc., until the games took place when he was 8 years old. That happened in 1991. This is a fact because Tom Hall/John Romero/John Carmack saw a young boy pogo-ing on the streets at that time, which instantly gave them the idea for the game. The first Keen game as we know was released on 14 Dec 1990. So we know Billy's age and in which year the things took place.
Yes, I know the games can still be pretty much situated in this year as well. And it will work well enough for sure. But given that Keen 1 was released in 1991 and is seen through Tom Hall's eyes (mostly) at that time, and the fact that the in-game story never mentioned which year exactly was the game taking place, we have but no choice to accept that the story took place in the very same year the game was released - 1991.
OK now looking at Suburb Shenanigans. We can see so many things that are not from the early 90's era. More specifically things like the big LED TVs, CFL light bulbs, robot vacuum cleaners...
I mean look at that giant 85+ inch monstrosity! Large screen TVs were developing rapidly in the late 90s. Yes, there were some led TVs before 1991, but never at that size, nor they were any good or that popular.
Or look at that all-electric Chevy Bolt:
There are many solar panels on the roofs of many buildings. They were not that popular back then and were almost impossible to be found on people's roofs.
And look at this guy, playing with his Apple Watch:
Have a look at that Portrait. This is Barack Obama. There's no way any pictures of him would have existed in so many homes back in 1991.
This all suggest that the Suburb Shenanigans mod is indeed taking place in the much more recent years. More specifically, it's taking place in 2018. So what is the explanation of all that and how is Billy still 8 years old then? The answer is simple: that's simply not Billy Blaze!
Commander Keen, the main playable character in this game, is actually not the Billy Blaze we all know from the 1991, but is in fact the child of Billy Blaze named after his father. You see, Billy Blaze has grown up from 8 years old in 1991 to 36 years old in 2018. What we see and play with is his son, Billy Blaze jr, who now takes place The Commander Keen role from his father. The home is now Billy's own home, and his son, Billy Jr, is using his childhood bedroom. Susan Blaze is Billy's life. Coincidentally, she's also named as Billy's mother. The posters we see in the kids room are still standing ones from Billy's childhood. The retro computers/TVs are relics collected from local stores such as Goodwills by thrifts.
So yeah. In this mod we play as Billy's son, Billy Blaze Jr, and the mod is taking place in the year 2018.