I'm in a fairly large clan on the PvE server and we tend to get brand new players a few times a week. Except some of the old vets that have played since 2016 I have yet to hear anything positive about the mechanics of this "Lost Fleet"
For the new players it has become a deterrent in the game rather than something positive. As stated above the result is
Always spawns close to server downtime for maintenance.
Always in the same select areas on the map.
Always looted within 30 minutes due to alts etc....
Rather than taking a Server Wide perspective on this where a few items are available for and to the entire server in a very limited time window change it to something more dynamic that is player centered and random times.
ANY player should have a chance to obtain "loot" from said shipwrecks. What they do find is random and not specifically always a Dead Man's chest or a Tuna or Bull Shark or Bottle of rum...but randomize for you own loot tables and limited to some sort of "Treasure". A Basic Ship Upgrade at a minimum.
This would provide not only random occurrences in general, as opposed to always 90 minutes before maintenance, but also encourages everyone to participate. This in turns creates conversations about who got lucky and who did not, positive outcomes rather than what pretty much at the moment is very negative to most players.
Just an idea