This is the full titled version of Reznicek's piece. The work is distinctively heavy in its 'serious' approach to the genre, moving far away from the light salon style of the 19th century.
At Henle 5 this is a late-intermediate piece — technically substantial, with musical demands to match. The main demands: careful pedaling — clarity depends on the foot as much as the fingers; sharp dynamic and character contrasts held together in one arc; and a true singing tone, with the melody floating above the accompaniment.
Beyond that, expect big chords that need weight without harshness.
Mastering the dense chordal texture while maintaining a cantabile melodic line is the primary hurdle.
Comparable difficulty and character — good candidates for what to learn next.
A level or two down with the same spirit — ideal if this piece is still out of reach.
Where this piece's skills lead: slightly harder works making similar technical demands.
Ernster Walzer für das Pianoforte is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 7.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of Ernster Walzer für das Pianoforte lasts about 5 minutes.
Ernster Walzer für das Pianoforte is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.
Pieces at a comparable difficulty and character include Ernster Walzer by Emil von Reznicek, Ciacona in F minor, P.43 by Johann Pachelbel, Der traurige Mönch by Franz Liszt — see the full similar-pieces list on this page.