Hard to add anything but as many have pointed out already the story quest themselves are not a problem. Getting there is.
Why we still have restrictions that were only put in to pad out content? If the content is not relevant anymore (aka not the newest shiny) consider lowering requirements (MR gates, tasks that required to complete, etc.) and make it easier for new and returning player to catch up. New war being an excelent example. Just remove the railjack and necramech requirements, lend a basic version of those for the duration of the quest and be done with it. The quest itself is not demanding at all.
This "10 years worth of content" is 10-15 hours of actual gameplay at best but even that has a lof of fat to be removed to make it more streamlined.
If someone has friends to help them out this makes little to no difference. It only depends on how much someone wants to be carried.
For new solo players the experience would be ruined. You even droped the whole Duviri path as a starting point after 3 months of introducing it so I have no clue why this is even a topic now. Unless it's a monetary driven idea ...
Creating a problem then selling the solution is not the way here. Fixing the root cause of the problem is the long term way to go.