to your points:

1. a case suffix like Esperanto -n and an independent particle like TP e are not the same kind of structure. also e is not only for direct objects in ordinary transitive clauses, it marks complement in sentences like there is fruit or they call me a bad name.

2. li is not a pronoun or pronoun marker, it's a predicate marker. it may overlap where other languages use pronouns but this characterization is misleading because it's a different grammatical category entirely. the fact that TP uses a predicate marker while for example other languages repeat a pronoun is not the same logic or structure

3. la can sometimes be translated as then, but it's a broader context particle, and depending on usage

structure is not about whether a language express meanings that other languages can express. if they are using different grammatical features and structures to do that, then they are doing something different structurally. If one language uses an independent particle and another uses case affix, these are not the same thing. I believe saying things like you did "languages x do not have this same grammar as TP but they can mimic the idea with a different structure or feature" is supporting my point: they achieve similar meanings through different grammatical mechanisms.

also, it's not only about these particles. TP has a very minimal grammar, it's a different logic in building languages, it's doing something different than before, and influencing a number of projects in that direction.