Clearly We don't share the view
For me "A mi abuelo va mal con su teléfono móvil" sounds bad, is wrong, but I can't think another meaning, and because of that I think if not everyone, almost everyone understand the right meaning.
I'd never said that "le" wasn't a pronoun, and yes is attached to the complement, "a mi abuelo" isn't a subject, you don't say "A mis abuelos les van mal con su móvil". "irle" is a especial contruction...
and why I think, in my opinion, can be more helpful to understand as a part of the verb...
first, I don't invent anything new, you can find many grammars where the pronoun in a pronominal verb is reffered as a part of the verb.(a example easy to find, the definition in wikilengua)
In the RAE (The Royal Spanish Academy,the official institution responsible for regulating the Spanish language ) you can find the following definition:
"pronombres personales átonos. 1. Formas. Los pronombres personales átonos son aquellos que funcionan como complemento verbal no preposicional (Ya te lo he dicho) o como formante de los verbos pronominales (Ahora me arrepiento). Precisamente por su carácter átono, se pronuncian necesariamente ligados al verbo, con el que forman una unidad acentual. Estos pronombres carentes de independencia fónica se denominan, en general, «clíticos» (?? acento, 1.1b): cuando anteceden al verbo (me encanta; lo dijo; se fue) se llaman «proclíticos»; cuando siguen al verbo (ayúdame, díselo, vete) se llaman «enclíticos»."
but, despite academics discussions far beyound the needs of a begginner, intermediate and even advanced learner, and more for philologists or linguists...
for me, is easier to understand thinking of a unit, thinking "le" isn't a indirect or direct complement, and because of that you need the rest of complements in the sentence...
...and learning as a unit with a specific meaning.
for example, I find easier learning phrasal verbs as differents verbs, better memorize "despegar"-> "take off", "llevarse" -> "take away", than "take is "tomar", adding off is "despegar", adding back...".
but each person has their method, and for you is easier see it in another way...
and maybe 21stcenturyphantom understands you explanation better than mine...
is funny arguing sometimes...
Saludos
and as a curiosity, french have the same pronominal verbs...