As I said it's not even really defending that needs the buff, personally I have no problem running back but it's about getting yourself in the right position and timing it right. I don't know what defenders people have but pace is not the issue really, it could probably do with a tiny tweak at most and that's me being generous. The only nerfs and buffs need to happen to timed finishing and goalkeeping. If your goalkeeper actually made saves you wouldn't care so much about the pace problem, my 93 rated Casillas is useless in almost every situation.
Timed finishing needs the nerf because the way it works seems to essentially nerf the keeper, the shot isn't realistically anymore accurate or powerful than a perfectly done precision shot, instead it just seems to make the keeper unable to save it instead. Add to that the fact people are abusing timed finishing with hacks and macros, and I'm sure you can see why it needs to go.
Lastly positions exist in football and shoehorning people into the wrong position rarely works out, that is why there are positions on fc and why your players can't do those roles so well. I'm not going to lie, if you feel like you need fullbacks at cb then you just can't defend that well in the first place, or you are playing a depth that your defenders shouldn't be playing. That's just user error, I can say that comfortably as a div2/div3 player. I'm not even that good anymore and I don't feel the need to have fullbacks at cb to match a run. I play against some of the best cards on a regular basis, and don't have anything I could think that most people would say is a meta card.
Please stop deflecting from the real issues in this game to complain about things that you just can't handle as a player. Goalkeepers need a buff, and/or timed finishing needs to go, it is literally as simple as that.