Williams have been getting progressively worse since Adrian Newey left the team; they’re now very short of money (compared to Ferrari, Red Bull & McLaren) and as such will probably never make it back to the top again without some major investment or a massive shake up of the rules.
It’s sad but the most likely future for the Williams team is one of mediocre mid-field finishes followed by a decline into oblivion, but then again this is the same thing that happened to most of the other teams that used to compete in F1, even some of the great ones.