Jund colored creatures are most likely to get trample, can't be blocked except by two or more creatures, etc.
All those colors already have those tools but they do different things than Intimidate. Bladetusk Boar is a totally different card (worse) with a different role with trample/can't be blocked excpet by two dudes.
They want to make sideboarding matter. Bladetusk Boar is "random" because it just says "if youre opponent isn't playing red, I'm probably unblockable. If they are, I'm not." They want cards that more consistently function the same in match to match. And for color-hosers, that means making them sideboard cards you bring in. Cards that turn off or on arbitrarily based on matchups with no intent required don't add skill to the game, they add luck/variance, and they add it in a place you probably don't want it.
Jund has flying in Black, Falter in Red, and Trample in Green, for evasion, btw.
If you're opponent isn't playing a certain subset of blue, white or green creatures then fliers are also unblockable. The distribution of fliers and reach creatures isn't equal across the colors so there is already a "color hosing" element. This really feels like trying to solve a problem that doesn't really exist. In certain matchups your intimidate dudes are near unblockable and in other they aren't. In certain matchups you fliers are unblockable and in other they aren't. I looked through Theros block and there are 67 creatures or cards that make creatures that can block a creature with flying (add 7 more if you include cards that grant flying or kill fliers directly) but there are 77 creatures (4 of them are Gods though) that can block a Bladeusk Boar. What's the big cause for concern?
I'm also aware that Jund colors have other "evasive" mechanics (trample is barely evasion) but they do different things than Intimidate and go on different creatures. "Falter" isn't a creature keyword so I'm not sure how that's relevant to the discussion. Stromblood Berserker is a good man but Viashino Runner is pretty trash as far as limited commons go - it's in the colors advantage to get "Snapping Drake" tier cards for limited.
Black makes great use of intimidate on creatures that for flavor reasons shouldn't have flying and are too small to use trample effectively (or also wouldn't have trample for flavor reasons - trample is rare in black be deafult). For Lifebane Zombie to have flying, it needs to be a Zombie Knight/Siren etc. instead of a Zombie Warrior. But what happens if you want it to be a Warrior or you don't want it to be a bird, siren, etc (WOTC does care about creature types outside of tribal blocks in design)? Intimidate opens you up to creative interpretations that flying does not (and vice versa of course).
Green probably needs intimidate the least but cards like Gastaf Howler aren't cards you can just slap trample on and call it a day.
TLDR: I disagree with the assertion that Intimidate is swingy enough in a way Flying isn't to be worth getting rid of the keyword given the design, development and flavor benefits it has.