Let me make this as transparent as possible. Here are all of the 4-3 teams and the snap % of their 3rd CB/5th DB vs a 3rd LB. The DBs snaps will be listed first...
Dallas 67% vs 28%
NY Giants 39% vs 55% (this number is skewed by Eli Apple getting traded mid season. If you combine Apple's numbers with his replacement you get 725 snaps or 66%)
Philly 5 CBs above 33% vs 31.6% (3rd CB was 52% but they had several CB injuries, so I wanted to show how many CBs got snaps over their 3rd LB)
Minnesota 54% vs 32%
Carolina 63% vs 59% (this number is heavily skewed by Carolina working Shaq Thompson into Thomas Davis role. Worth pointing out that Thompson was a first round pick as a third LB who has never played as many snaps as Anthony Brown did in 2018)
Tampa 40% vs 35% (these numbers should be thrown out considering the number of injuries at CB and LB)
Atlanta 76% vs 48%
New Orleans 59% vs 47%
Seattle 67% vs 28%
Arizona 50% vs 32% (they used 3 safeties more often than not as opposed to a 3rd CB)
San Francisco 55% vs 31%
New England 61% vs 31% (also opted for a 3rd safety over a 3rd CB)
Miami 73% vs 62% (also opted for 3rd safety over a 3rd CB...Minkah Fitzpatrick was technically both)
Buffalo 44% vs 62% (here is one of the few examples of a good defense using a 3rd LB more than a 3rd CB/S)
Cleveland 55% vs 58% (skewed by injuries again. Several DBs in the 40s and 30s that lowered that 55% down)
Cincinnati 60% vs 45%
Indianapolis 42% vs 37% (I had to combine the 3rd and 4th LB to get to 37%, obviously an injury, but data is consistent with my point)
Jacksonville 44% vs 14%
LA Chargers 60% vs 25% (had a 3rd safety at 66% that I didn't include)
Oakland 49% vs 40%
So across the league, 3rd CBs/Safeties are getting 50%-65% of defensive snaps and your 3rd LBs are getting between 30%-45% of. There are a few outliers, like Buffalo and Cleveland, but I would suggest looking at similar schemes as ours. Seattle is near identical, Atlanta is even more skewed towards using a 5th DB over a 3rd LB. Even Jacksonville's d-coordinator spent 2 years in Seattle and they use their 3rd-5th LBs for a combines 22% of snaps (6th and 7th LB played 0 snaps). So this has nothing to do with Darron Lee and everything to do with scheme.