Different formulations of the teachings support people facing different conditions and circumstances; this can be appreciated and valued.
You should not always assume that your school is the best to enrol other people in, that's just another form of Dharma-bashing: “my school is best, no matter your conditions.”
To be able to send people to another school, better suited for their circumstances, embodies wiser care than to always assume your school is appropriate. But to send others to the appropriate school, you need to know enough about the schools available!
Hopefully, the analysis on
interpreting the teachings might have convinced some Theravādins that
their tradition strongly supports a mindful and healthy curiosity, including
towards the reformulations (which might initially appear as
“surprisingly loose”) by Mahāyāna and Vajrayāna
Hopefully, it might also have convinced some followers of the later schools that Theravāda is not to be overlooked as ‘simple’, and that Theravāda did directly address ambiguities and subtleties! It's easy —but delusional— to imagine Mahāyāna as ‘superior’ due to the piling up of hyperbolic elaborations and interpretations; in fact, Theravāda issued the calls for subtle enquiries, for precepts not to be taken literally, for a nuanced understanding of dependency on a context, for an attention to potential exceptions (without falling in their pointless pre-conception —mental proliferations! —nor their pre-listing in the rules). Zen students may remember that the first Indian patriarchs of Zen were… Mahākāśyapa and Ānanda!
There's no valid claim of superiority between the Buddhist schools, only delusions!
There's no valid claim of ‘fundamental’ separateness between the Buddhist schools: either delusions, or simply different manifestations of the same core made suitable for different circumstances!
Rejecting forms of Buddhism as “other religions”
is just a disguised attempt to ‘own’ the “Buddhism”
label (because, of course, once the schools are separated, yours will
be ‘Buddhism’ while others’ will be
e.g. ‘Śākyamunism’ or
“This is mine” is a prime recipe for “self view” though, i.e. for perpetual suffering!
There's no valid claim of ‘fundamental’ separateness between the Buddhist schools, the nuances in “expedient means” are variations on the same Liberating theme!
A common mistake on the spiritual path is to separate yourself from your potential (i.e. your ‘buddha-nature’). Training, trusting your buddha-nature is possible though, a three-fold training in morality, meditation and wisdom.