Space-time interval...

What is the space-time interval?
To describe it, mathematically, and not semantically,
because it may be an abstract construction requiring a complex number, we use the formula ds²=dl²-dt².
That doesn't make the "thing" much clearer.
We can then set ds²=dl²+i²dt²
But that doesn't make things any less clear.
I suggested setting fire to all that, not to bother with it anymore, to leave the student alone for a while, and to never again use this ridiculous, heavy and cumbersome notion in special relativity.
We don't have it, and that's also what's terrible, despite the cries of some aficionados who have no need for it.
So why this stupid fanaticism?
Stockholm syndrome? The persecuted ends up adoring and glorifying his tormentor?
What's the point of all this?
R.H.