Luna is trash and people who pick her are throwing.

[The adventures of Lyonic!]

Luna is one of these hero's where she really is terrible in pub games and everytime I have a luna on my team, I always lose.

She has stupidly short range, so lacks the ability to do any kind of meaningful kiting.
She has split damage physical/magical, which makes buying items difficult
She has zero basekit mobility, any good CC, her glaives are useless in 1v1s.

[Zagryzaec]

No ranged carry can properly manfight meelee carries nor kite vs basher.
Her balanced damage allows to adapt to situation and destroy both magically and physically resistant targets. Just her aghs ult+refresh can kill half the team before fight even begins unless they use/waste bkb.
Her base speed allow her great mobility without items and even better with items her glaives giving her ability to both farm and push intensively to get those items and her aghs ult with talent basically permastun single targets unless they can bkb

[ダリア]

According to dota pro tracker luna 50.6% winrate
Is she that bad? Not really obviously she is not a meta hero more like tier 3 hero with very situational pick and very strict draft so she work well in some draft
Luna + visage is good example you have very strong early - mid game because of free damage aura that work with visage ultimate
Luna is not a hard carry since 3 of the ability is fix number that cant be increase by item
The reason you alway lose with luna in team because the draft doesnt go along with luna if you team are picking luna it mean they want mid-early game timing roshan and snowball
If you team keep farming with luna in team without using the free damage aura to fight or take tower you obviously lose because she cant fight meta hard carry like faceless void or even terrorblade(which is tier 2 hero)
So luna is not a trash hero but it because of draft doesnt go along with her