I'm with you 100% on the resources point. đź‘Ť
I'ld rather see that time put into 2 (or maybe 3?) short real tracks.
But I have an alternate view on your other point.
For me, Sierra lost favour rather quickly.
It was a track I didn't drive very often, so I felt lost.
And it snowballed from there.
But the more casual players loved it, and went there more to just stuff around than actually racing or pushing lap times.
And occasionally when I was bored I raced there, and got whipped.
I don't imagine there would be many Sports Mode events held on it, for the reasons you mentioned.
But I can see the "cruising" lobby or "cops and robbers" lobby players absolutely loving IoM.