Of course, we shouldn't think that those aforementioned altars with those wonderful canopies and antependia were representative of the usual quality or standard of sacred art in parishes at that time; in point of fact, they were likely a great deal better than what was often found within the typical parish -- which brings me to the subject which I wished to discuss today.
Often times what is popularly viewed as "traditional art" or even a "traditional church" -- and I think now specifically of church interiors and of churches outside of continental Europe's historic churches -- is defined in great part by the liturgical and devotional art of latter 19th and early 20th centuries; mass produced art which is often mediocre at best. Of course, I do not wish to generalize about the entire period; there are particular pieces or artisans from this period who stand above this of course -- one can think of Gothic revivalists like Pugin, Bodley or Comper for instance.

Turning back to the aforementioned transition, it seems that one of the underlying motivators which influenced some of the developments in 20th century liturgical art was a desire to rise above this sort of mass-produced, rather sentimentalist, not terribly qualitative sacred art. Here I am specifically thinking of the materials used and the approach to them. Altars, whatever one might think of some of the designs used during this period, often employed real and substantive stone. Statues, while often rather primitivist in form, were carved and made out of real wood or real stone at that. Instead of plaster reliefs with electric lighting on altars, we saw mosaic work or carving. In short, there was an apparent emphasis on a certain authenticity and quality of material, as well as on craftsmanship -- and I should note that I am primarily focusing here on the earlier incarnations of this movement; as we move into the post-conciliar period, I believe we would find the results more mixed.
Whatever the other faults to be found in many of the extant examples modern liturgical art, I believe we have to look at this particular aspect with admiration. The unfortunate influence of an avant-garde primitivism indeed marred the form of much of what was actually produced during the period, but the aforementioned aspirations and principles are something worthy of emulation. Accordingly, we shouldn't let the stylistic accidents of many expressions of the modern period distract us from what were otherwise worthy underlying ideals for sacred art, nor allow it to influence us to retreat to or setup what came immediately prior as some sort of standard and exemplar.
In point of fact, such ideals of craftsmanship and qualitative materials are very much rooted within and representative of the tradition of Catholic sacred art. If we can put those ideals into practice today -- overcoming the strong modern tendency of an economically driven and generally commercialized, mass-produced view of art -- and further combine that with a stylistic approach (whatever that might be) which is characterized by continuity with our tradition, we would serve the Church and the liturgy well indeed.