I have had this argument a few too many times.
The big thing I will say is that two of the big reasons people seem to want to nerf Lithuania's development are;
1) because they dislike them being Second in development to France.
The issue here is that development is completely out of sync and highlighting Lithuania alone is unfair. Iberia has much greater development than it should compared to its population, as does Scandinavia and England. France and most of the rest of the world have far less developments than they should. There is very little actual match between population and development, in that respect Lithuania is far from the worst offender.
2) Because they are to strong compared to Muscovy
This is simply not true. In 1444 Lithuania is significantly stronger than Muscovy, true, but if you expand historically as them up until 1500 (which is much easier than history because the hordes are much weaker in Eu4) then Muscovy actually becomes much stronger than Lithuania. At the point historically where Muscovy defeated Lithuania, they actually have much more development than them and can field bigger armies, even though historically the wars were not as one sided as some people like to make out (and involved allies).
I actually think that Lithuania's development is entirely reasonable for the area, it in fact balances fairly with other powers in the region. I don't think they are too strong compared to historically either.