Hi chaps

I recently rented the BR of The Lost City of Z, and found the sound very muffled on my 5.1 system. It clearly wasn't in 5.1, and sounded pretty awful with the DTS track selected. This is via my PS4, which normally produces DD 5.1 and DTS soundtracks without issue.

My sound comes from an admittedly ancient 15 odd year old Pioneer system-in-a-box with a an integrated DVD player/amp, 5 satellites and a subwoofer. I've used it for many years with DTS and DD 5.1 games and Blu-Rays via its lone optical input.

Naturally given its age, it doesn't support Dolby HD or DTS HD (and of course, forget about Atmos and DTS X!).

Consulting the Lost City of Z disc, it only has a DTS HD logo. That was the only option in the disc settings too, apart from stereo.

My question: is old school DD 5.1 and DTS now being phased out on BRs in favour of the HD formats?

It's the first disc I've ever encountered that doesn't seem to support the older digital formats