A couple of the teams that are crushing you have artificially low ratings because of taking walk-ons. Their 11-man rotation averages much higher than your 11-man rotation. But let's take a test case of a team that's not like that, has a similar rating, and killed you: Denison.
You have a three-point edge on overall rating, but you should look at some of the individual categories:
*They have a 20-point ATH edge.
*They have a 10-point SPD edge
*They have a 13-point DEF edge.
*They have a 17-point PER edge.
*They have a 13-point BH edge
*They have a 9-point PASS edge
*You have a 16-point REB edge.
*You have a 21-point BLK edge.
*You have a 20-point LP edge.
*You have a 4-point WE edge
*You have a 6-point STA edge
*You have a 17-point DUR edge
So how should the game play out, if we just think a real life game with these characteristics (that's not a wonderful proxy for how WIS games work, but it's a good start to a thought experiment)?
*Unfortunately for you, they have a huge advantage in both speed and athleticism. A slow and unathletic team can beat a speedy, athletic team, but they need to have big edges almost everywhere else. You have edges in a few places, but not enough. Your speed and athleticism affects your entire game. For instance, without powerful guys with good leaping ability, it'll be hard to take advantage of your edge in rebuilding technique.They can have worse technique but just out-athlete you. ATH is one of the most important ratings in the game.
*You have an edge in rebounding, which should allow you to win on the glass, but their athleticism might cancel it out to some degree.
*You have an edge in shot blocking. I have no idea whether this is important. But it might be canceled out by athleticism in the same way as REB.
*They have an edge in defense, and you're about the same in the combination of scoring ratings (LP/PER), so they'll likely shoot a much higher percentage than you. You may have an edge inside, but their perimeter shooting will crush your bad perimeter D, and I'd expect to give up a lot of threes.
*They handle the ball MUCH better than you, and since both teams run the press, that means they'll likely avoid turnovers while you commit a lot of turnovers.
*You have a big edge in durability, which means you're less likely to get injured during the game. But because injuries don't happen that often, this is not likely to be important.
That's my analysis just looking at ratings in each area, without even looking at who the starters and subs are (which is obviously quite important), let alone opening the box score. After opening the box score:
*You won the rebounding battle by OREB%, but just barely. Their ATH canceled out your REB. Because they took more shots, they got more total rebounds, but this facet was almost dead even (you got 40% of your misses, they got 39%)
*They shot six percentage points better than you from the field. Makes sense because of their D. You actually didn't get burned too bad from deep though.
*They won the turnover battle in a BIG way. This contributed to them taking seven more FGs and 11 more FTs than you. This is because of their BH/Pass advantage on offense and their SPD/DEF advantage on D.
Does that all make sense? I know it's a lot, but it's better to break a game down like this than just looking at overall rating. And it's even better to break your game down by looking at the individual matchups. You're better off having six guys with 99 PER and six guys with 1 than having twelve guys with 50 PER, if that makes sense. So even the average ratings for each skill aren't the be all and end all.
But I hope this gives you a better idea of what to look for. My main advice would be to seriously upgrade your speed, athleticism, and defense in recruiting. Don't worry at all about durability. Also read aejones' "How to win at D2 and D3" thread.