It goes without saying that ENT was a missed opportunity for all the reasons you mentioned and more. I felt the same way about DS9 and VOY.
As for the Xindi arc, I believe a political hand was involved with that one. The President of Paramount met with Bush and Congressional leaders following 9-11 on the pretext of making "television more responsible". The result was public announcements by Bakula welcoming the return of U.S. aircraft carriers and well, the Xindi arc, which was a reflection of the foreign policy the U. S. was pursuing at the time. I tuned out ENT because of this.
Art shouldn't be politically used to advance the agenda of those presently holding power. It should explore the timeless human condition in all circumstances and scenarios. Besides, ST has always been a little left leaning; the first interacial kiss, the first lesbian kiss, etc. Even Roddenberry's vision of the future is non-status quo.
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