The problem was Rick Berman and Michael Piller.
And I think you meant:
Had they NOT gone this route, this would not be the last season.
The stuff this year after Berman moved on has been quite good, particularly the multi show story arcs. I've read that the season/series finale is really disappointing, and that everyone is blaming Berman, who came back to write it.
"And then the little boy woke up" so to speak. Not quite Bobby Ewing stepping out of the shower, but apparently not far off, either.
Enterprise was DEAD before the Xindi Arc... by season 2 it had shown it was flailing going nowhere. PC lectures, limp wristed "social conscious" captain... What should have been a mans man leading a manly crew out into the unknown was turned into a bunch of wusses tied up in nonsense.
Andromeda was great the first few seasons... once they had the commonwealth recreated though... went down hill big time...