Linguistic change is always a change in the linguistic system, a change in grammar. While vocabulary changes relatively fast, linguistic shifts can only be traced in the process of changes in the components of grammar: morphology, phonetics and syntax.
Languages neither become simpler nor more complex. This is true of the contemporary Hungarian language, which is not less (or more) complex than Old Hungarian.
There is no relationship between language change and those using them. Naturally, vocabulary is affected by the changes in society and civilisation but from a linguistic point of view this is peripheral. The grammar, the system of the language itself, does not reflect anything. It is an arbitrary code, which does not need to have the same configuration as the messages it conveys.
Linguistic changes do not have reasons. Language changes because, within certain limits, there are no obstacles to generations or regions modifying it. In any case they modify only as much as necessary without being detrimental to communication. The notion of language corruption therefore is an unscientific nonsense, as it does not recognise the fundamental nature of language and thinks of it in human and moral terms.