i'm 30 yo, received transmission at 16 or 17, and practiced very very seriously since then. Said that, i can see with a good grade of certainty that the main problems for the future can be found:
1) in the lama's attitudes towards western society
2) in the older students attitude towards new students
in general, lamas do like to fantasize that they still are in tibet. well maybe they don't know that i'm a westener and i'm not interested in tibetan manners... in fact i give exactly 0 f*cks on tibetan culture. If dharma comes in chinese then i learn chinese, i do care on dharma but i don't care much from where the lama comes, don't find anything special in tibetan culture. so the tibetan stuff can turn to be an over whelming obstacle for new buddhists (language, manners, traditions, etc.) when lamas do everything pretending that they are surrounded by tibetans. tibetan stuff is not the main point.
as i was younger i had to took a lot of shit in my intents for gaining access to the teachings, shit like old practitioners phantasies, old practitioners not helping new practitioners, not having to whom ask anything about experiences, old practitioners behaving like kids/adolescents, not having access to books, old practitioners arguing, discussing, etc., old practitioners not having boddhicitta, having no money to study (because yes, you need money to study tibetan buddhism or participate in sangha activities), old practitioners talking only between themselves, etc. Such thing of course that discourages young people and new practitioners.
this are my arguments haha, sorry
now there are issues, like what's more important ¿donation or boddhicitta? (is money what the lama really want?), the why there is infraestructure for each lama in each city (why don they share if they are enligthened?), spiritual ego (does tulku or rinpoche means something, why they travel in 1st class, why they dress in silk?), etc., such things makes think that this buddhism is just like profit oriented religion..
no need to mention the sexual -and other- scandals...
"Don't profess a view you haven't realized!
Since the view is devoid of viewing, mind essence is an expanse of great emptiness.
Since the meditation is without meditating, leave your individual experience free from fixation.
Since the conduct is without acting, it is unfabricated naturalness.
Since the fruition is without abandoning or achieving, it is the dharmakaya of great bliss.
These four sentences are words from my heart:
Contradict them and you fail to discover the nature of Ati Yoga."
From "Advice from the Lotus-Born".