What do you think about the melodic death metal genre?

This subgenre of death metal is actually quite good on its own. But it becomes less appealing when my favorite thrash metal bands start incorporating its elements. For example, Kreator. They started by playing top-notch German thrash, then experimented with gothic elements, and now they continue to play thrash with a significant dose of Swedish-Finnish melodic death metal. I'm afraid this will also be the case in their upcoming new album.

I've always liked "Sodom." And I was sure they were playing MDM (especially in their later albums). But I keep being told that it's thrash. I don't understand, where's the thrash? It's melodic!

Sodom never played melodic death metal. Their first EP and first full-length album were actually prototypes of traditional black metal. Subsequent albums were top-notch Teutonic thrash metal. Starting with "Get What You Deserve" (1994) and ending with "'Til Death Do Us Unite" – crossover thrash. From "Code Red" to the present day, they've returned to Teutonic thrash, with few elements of MDM.