The Samputa states:
None of the eighty four thousand Dharmaskandhas
have any result since the true state of the body is not understood.
Since the true state of the body is not taught outside of highest yoga tantra, etc., well then, I leave you to your own conclusions.
Now then, Ngorchen does clarify in his commentary on kriya tantra that the most a person can aspire to with kriya tantra practice is the tenth bhumi:
"The result accomplished in one life of anuttaratantra is only the perfect Buddhahood of the three inseparable kāyas; here, having relied on the three paths, one can manifest the tenth stage in this [life] and with that support, Buddhahood can be accomplished."
He also explains that even so, the path of kriya tantra is quite slow:
But in kriya tantra, because there is no teaching of taking siddhis apart from (40/a) inviting and creating the deity in front, the speed with which the result is accomplished is slight. The difference with Pāramitāyāna is very important, in that in [Pāramitāyāna] not even taking siddhis from a deity invited in front is ever taught.
Further, the difficulty with kriya tantra is that it is very precise and requires absolute adherence to ritual purity and so on. This is quite difficult to maintain unless you are in a place like Koyasan, etc. For all of these reasons then it is safe to say that for the most part we can consider kriya tantra ineffective in this day and age (which was my point), which also explains why outside of Shingon and Tendai, no one practices it anymore. There is also the consideration of which yuga a given teaching is most effective or needed, and in this yuga, the kali yuga, annuttarayoga tantra is a desiderata.
Yet nobody says the lower tantra path is as easy as the higher tantra path. Lack of difficulties is precisely one of four superiorities of tantra over paramitayana, and by implication of the higher over the lower paths. There is superior and inferior, but not effective and ineffective, and superior means the four superiorities. E.g. Loppon Sonam Tsemo on the superiority of methods:
For Guhyamantra, there are immeasurable methods of accomplishment sadhanas such as Manjushri and Vasudhara which can be accomplished without difficulty and become a support for the bodhi-mind.
It is a reference to the siddhis these deities bestow a superior method that is absent on the paramita path.
When he says that only Guyhamantra is appropriate for the present times, he is not referring to 2014 or to any specific place such as Koyasan, but to the Kali Yuga. This is very clear. In Sakya, it is held that Sachen achieved realization in dependence upon Manjushri and Achala in the degenerate age.