Question 1 - what are these other conditions?
One example might be the chronological and cultural distance we have from the texts, which earlier populations experienced differently, or even not at all when one goes back far enough.
Question 2 - why & how are they different to causes in the time of the Buddha?
The words used, the implicit understandings which were part and parcel of that milieu, the off-hand remarks and idiomatic expressions referring to a connotative realm wholly foreign to us today, all of this contributes to the distance mentioned in Q1.
Question 3 - how & why are the teachings disproved, irrelevant, not appropriate due to these new conditions?
The teachings, overall, require a careful approach in order to make salient the presuppositions and assumptions one brings to them, but this has probably always been true. I think the field is simply different, rather than better or worse, so the teachings are not necessarily disproved, irrelevant, or inappropriate due to this, but changes in emphasis can certainly be seen (in the West, meditation over merit-making, for example).
Question 4 - how is this outside world more materialistic/worse for practice/what ever else you believe it to be, and how does that change things in regard to the teachings & practice?
I think access to the internet and television and personal music players are all worth mentioning; the barrage of entertainment is certainly greater. The world is now largely one of readers, not oral traditions, which changes pedagogical approaches to the Dhamma. Most people have a fundamental outlook which is based on modern science, which gives them an altogether different world view about how things work. Other examples can be mentioned, but they are in alignment with being mere differences, per Q3.
Question 5 - how are we different (in relation to the Buddhas teachings & practice) to people back when the teachings took place? and why does this matter?
World-view as above, the linguistic differences which change how experience and conversation is naturally framed, and lack of familiarity with the colloquialisms of the day are all differences which increase the need for careful scrutiny of the texts.
It isn't necessarily easier or harder to get at the Dhamma, just different.