Welcome to the Forum, Skill-Junkie:
Texture was used extensively in the 70s and 80s to cover up a half done finishing job. Some people would use 1 coat and the tape and texture without even sanding.
I think your easiest option is to just knock down the high spots and trowel it out with more compound. To try to sand the whole texture job off will produce unbelievable amounts of dust but, if you try to fill out the whole job with compound, you'll be adding several buckets (and pounds) of compound which will crack if it is not spread in thin coats and allowed to cure well after each coat. Some pictures of this job should be good entertainment.