How easy is the task of creating a long post without making use of pronouns?

Not easy at all. Pronouns are like nuts and bolts in a large contraption — metaphorically, grammar. Very useful.

Especially confounding is the following fact: words can belong to multiple
parts of speech, being polymorphic. As a rule, no polymorphic pronouns are
used here. Just for fun.

Consequently, several natural idioms are precluded from use, severely
deforming the tone of the text, worsening as the length increases.

A programmer would relate, if given a similar rule: to not use local variables
in code. Lexical referencing is a powerful technique to have; otherwise
unnatural protracted constructs result.

Fortunately, however, not all referencing is lost without pronouns.
Adverbs can pick up the slack a little. For example, “here”, “thus”, etc are
helpful. Similarly with prepositions (strongly encouraging spatial thinking, for example: see below).

Perhaps circumventing the rules, as described above, makes the exercise too easy.
How about disallowing adverbs or prepositions too?

No wait. Sod that.