What Tarkovsky does with duration is so specific that I think it requires its own vocabulary.

His films — Andrei Rublev, Solaris, Stalker, The Sacrifice — are all long and all slow in a way that provokes the word 'boring' from viewers who aren't prepared for them. But the duration is doing something specific, not absent.

Tarkovsky believed that cinema's unique capability was its relationship with time — not the representation of time but the actual experience of time passing. He called it 'sculpting in time.' His long takes don't hold on subjects because nothing is happening. They hold because he wants the viewer to exhaust their interpretive instincts and arrive at pure experience.

The famous shot of the dog walking through the room in Stalker — it lasts long enough that you stop wondering what it means and start watching it. That transition, from interpretation to attention, is what Tarkovsky wanted. Whether you find it profound or interminable depends entirely on whether you're willing to make that transition.