Oh what the heck.
First off, you're making a non sequitur. The fact that Scorpion was ultimately a non-factor in UMK3's popularity does not in any way change the fact that UMK3's existence was chiefly caused by fan backlash at Scorpion's absence.
Second, in my opinion UMK3 ISN'T the only tournament-worthy game in the series. The reason that it's the only one being played at tourneys is simply because more people agree with you than with me. That doesn't make me wrong... it's called OPINION.
Adding characters, combos, and fatalities without making any changes to the game itself is not an improvement. It's just an expansion pack. They could have just left it alone and worked on MK4. The only reason UMK3 was made was because the Scorpion fanboy nation is so big that it actually made economic sense for Midway to appease them.
And I have played the following MK games: MKI, MKII, MK3, UMK3, MKDA, MKD. I have not played any of the games outside the main series, nor have I played MK4 or MKA, largely because their releases coincide with my periods of less interest in MK (I'm somewhat cyclical in that regard). I believe I've played enough MK games to offer an OPINION that I don't like UMK3.