I still don't buy this. You said yourself you liked the show, I (and many others) have said they enjoyed the show. If the point is to entertain viewers, then obviously the plot was sustainable.
The plot (TNG 2.0) they ultimately went with got them viewership, the original "Lost Ship" plotline (which they get critiqued for abandoning) wasn't sustainable.
Let's look at ever "Lost Ship" show from the last 40 years worth remembering:
Blakes Seven: Had more to it than the "Lost Ship" thing from day one, never had to deal with Repair issues or resupply, had a small cast.
Each season only had 13 episodes or so, which made the serialization easier. Show intended to end after 3 seasons, got one extra and still ended after 4.
LEXX: Only had 4 or so characters. Ship didn't need resupply or external aid, show ended after 4 seasons. Only had about 60 episodes. They dropped the "Lost Ship" thing after the 2nd season and spent the 3rd season in Heaven and Hell with the 4th season on Earth.
Farscape: Only had 5 or so characters at a time. Ship rarely if ever needed external aid or resupply. The dropped the "Lost Ship" thing at the end of Season 1 and had the rest of it be about the Peacekeeper/Scarran war and the search for Wormhole weapons. Barely made it to 4 seasons.
NuBSG: Had an entire armada, not one ship. Lots of spare cannon fodder to kill off without harming Galactica. Whenever things got bad they pulled a solution out of Deus Ex Machina (spare Battlestar, Renegade Cylons, "God"). Show fell apart after 2 seasons, rot set in by 3rd, show ended on literal Deus Ex Machina in 4th.
None made it past 4 seasons, and each one dropped the "Lost Ship" thing or had more to it from the start.