How is the Nebula-Class obsolete? By that same reasoning so is the Galaxy-Class (not to mention the Excelsior's and Miranda's that basically are the fleet).
In a reboot of Voyager I have on my computer, the Hera was pulled into the DQ but had to abandon their attempt to use the Array to get home when a Kazon Sect war erupted in the system. Not long into their journey they discovered an active Vaudwaar conduit and used it, but after several thousand light-years it destabilised and threw them out which caused a warp core breach. Evacuating to the saucer the crew managed to land on an L-Class planet, which became their home, using shuttles to travel to nearby systems for supplies and resources, whilst also starting to build up a small league of friendly worlds (the basis on a Mini-UFP). Voyager, after coming out of the un-reset Year of Hell, landed on a planet to make repairs and tend to wounded, also using shuttles to gather what they needed. On a trading station they learn from a merchant that they aren't the first Starfleet they have encountered and secure locations of other worlds that they've been known to visit. Getting the ship barely operational, they go out in search of the other crew and ultimately find the Hera Colony. There they manage to get help repairing the ship, restock on shuttles and torpedoes, as well as take on a few crewmembers to help fill the ranks of those who were most, though Voyager isn't large enough to evacuate the whole crew. After the ship returns home at the beginning of Season 7 (not thanks to Borg Ex Machina) the crew manage to raise a small task force to return back for those they left behind at the colony.