Keep in mind that LB play improved after they used a third to get the short term rental Fowler. Which supports the idea that they really should have put some decent resources into the LB squad from the start.
But yes, I think that better linebacking might have made a difference in the Super Bowl. Cut a drive or two short, and maybe the defense isn't exhausted at the end of the game. Have a thumper in the middle, and maybe they need to pass more, and somebody gets to Brady or a pass gets intercepted at a key time or the Rams just have a short field.
Ebukam might be better next year - don't know if he will ever actually be a good starter though. If the rest of the linebacking group was fine, not a big deal, but again for last season they were counting on some of these kids or longshots producing more than actually happened. And if your plan to address the linebackers is to start taking them at pick 160 and later - you're really planning to fail at that, or counting on an unrealistic hit rate for 2018. I would hope that at least some of the kids and the 2018 draftees would be improved in 2019. I still want a vet in the middle the team can count on.
If they move Littleton to Barron's spot, and put a thumper next to him, he might improve. I don't know if he has a bunch of upward room to improve, but what caught the coaches eyes were in 2017 when he filled in at most practices the second half of the season for Barron, so it stands to reason that he might be better than average at that spot, especially with a hard hitter next to him to allow Littleton to do what he does best.
I'm not trying to rip on the coaches, but while they did a good job building up a lot of the team, they tore down the linebackers and felt they could get decent work out of them without using any significant resources, and predictably that turned out to be wrong.