When looking at opening movements of instrumental concerti in the eighteenth and nineteenth centuries, we see a pretty standard alternation of ritornello (orchestral-focused) and solo sections. These are often (although not always) in a seven-part rotation of RSRSRSR that aligns with the expected sonata-form of the first movement. Occasionally one of these sections will be very short—Mozart's third ritornello section is often only a few measures before it gives way to the third solo section—but the seven-part structure is still obviously present.
But it's relatively rare for me to sense that form in more modern concerti. Even as early as Dvořák's Violin Concerto (1879), I have a hard time tracking the ritornello/solo alternations in a way that aligns with prior practice. When I look at something like the Vaughan Williams Tuba Concerto, it's hard for me to see this ritornello/solo pattern or an underlying sense of sonata form in the first movement.
Do opening movements of 20th- and 21st-century concerti still follow the ritornello/solo pattern or the expected sonata form of the 18th and 19th centuries? Are there genre-specific patterns for these opening movements that a listener can use to better understand the piece?