if Zelda can have his own timeline why cant Mario too? i will loved too see a Canon in the Mario franchise i think we're all sure Donkey Kong will be the first game chronologically in the list
This was already pointed out to you, but to make it more explicit: the protagonist's name in Legend of Zelda is Link, not Zelda. Zelda is the princess of Hyrule who goes by she/her pronouns. Haha.
Anyway, on-subject, I do believe that it's less that Miyamoto's busy and more that Mario himself is supposed to be malleable and multi-genre; he's designed with universal appeal, unlike Legend of Zelda, which has a more strict format. In addition to that, the vagueness of the timeline allows them to get away with things like SMB3's stageplay aesthetic, where one could theorize the entire thing is just a play that Mario is putting on for his friends to watch (or even someone acting as him?). It's less that Mario
can't have a timeline and more that it is both unnecessary and would end up pigeonholing some of the plot threads.
Some games do have a loose timeline between them in through references toward each other. The Mario & Luigi RPG series is a good example of this, as the next in the series often makes reference to the one that came before it. Paper Mario is a little less explicit about this, but you can logically assume that every game within it comes in order. It should also be noted that as of Paper Jam, it's been made canon that Paper Mario exists as a story within the Mario & Luigi RPG universe (note: this doesn't mean the events of Paper Mario aren't real, just that they exist in storybooks in Mario & Luigi specifically). I think it can also be assumed every sports game follows this chronological order, too. Paper Mario 64 in particular likely takes place after the first two Mario Parties at the very least, because Luigi makes explicit reference to them in his diary. If you go with the logical follow-through that Mario & Luigi have PM as a story within its lore, that would place the M&L series ahead of those games, too.
There are some contradictory elements, though. Firstly, in Super Paper Mario, Bowser correctly identifies Luigi as Luigi by name (he greets him as Luigi if you come to find Bowser while currently playing as him), which, if you assume Dream Team comes after SPM's story would be published within M&L's narrative, makes no sense as that is the first game where Bowser finally acknowledges him. Even the little thread that has been created within M&L's timeline has therefore created a bit of an inconsistency issue, as apparently Luigi is well-known enough to have his name correctly identified within a story, but not when his main foe alongside Mario sees him in person. Simply put: these two series were never written to be meshed together, and it results in weird writing inconsistencies as a result.
This is a good example of why "timelines" in Mario should be kept mostly to direct sequels, because details like this will crop up as problems. And before you suggest that this particular detail is a minor one, not so: Luigi gaining recognition is a very big part of Dream Team's plot, and undermining it by suggesting he was
already well known, just for some reason Bowser didn't call him by name, throws off Dream Team's emotional significance. (We could go into how Paper Jam
in general undercuts Dream Team's development of Luigi, but that's a story for another thread.) This kind of changing of the timeline can retroactively hurt previous games, specifically the more story-driven ones.