he definitely is a hyper-scaling champion and his presence, if fed or lategame, can make a normally beatable team almost unkillable because later on, his damage is absurd and he is almost unkillable. if you focus him with ignite and your entire team, you will lose 100% because that is exactly what he wants.
vlads main weakness is in the earlygame and laning phase and the fact that he doesnt hyperscale in 1on1 scenarios, so you can still splitpush and out duel him with many champions.
he is a very strong and scary teamfighter past 3-4 items and he doesnt stop scaling. many even hyperscaling champs fall off after 4-5ish items because there are no more "optimal" items for them to buy, but vlad doesnt. he has plenty of optimal items he can choose from. as i said, his weakness is in the earlygame and laning phase and strong champions can make sure he never gets anything ever because he is in fact so weak against some champions that he cannot even lane properly.
so yes, you are right and your friend should not play rankeds.