You're being a little disingenuous. It describes the ARM architecture as 'elegant', and 1/4 of the way through the article describes the common use of fixed len

You're being a little disingenuous. It describes the ARM architecture as 'elegant', and 1/4 of the way through the article describes the common use of fixed length instructions in various RISC architectures as 'a good design', and explains why this is mostly a win. And then it explains how the ARM manages to encode a wide range of useful immediate values using a very elegant and simple scheme. In all my years coding in ARM assembly language, the range of immediate values it supported was rarely if ever an issue.