I'd agree toki pona is unlikely to be as mind-expanding as Lojban, but the kind of creativity that you mention, working within constraints, can be "mind-expanding" too -- just as composing poetry within a specific form, or practicing constrained writing, can be.

Even though there are some fundamental designed-in limitations in toki pona (for example, we don't officially have comparatives, relative clauses, or quotation! you can say "a is a little x and b is very x" or use a kind of formula with "x this: y"), it can be surprising how many things can be expressed reasonably well given the effort.