So, the one area that's causing me to keep mine is multichannel surround decoding; if your smart TV isn't that smart, a BR player that does do it (and has analog multichannel outputs, if needed) is handy to have (also for BR audio discs).
I just setup an ATMOS system in my media room and I have been buying DTS and ATMOS bluray media. I do have sampler media files also to play for demonstrations. Some streaming services only offer Digital Plus encoding, so the sound is not as intense as with physical media. From
https://developer.dolby.com: Dolby Atmos audio in Dolby Digital Plus is typically encoded at bitrates between 384 and 768 kbps. Dolby TrueHD bitrates average around 6,000 kbps for Dolby Atmos at 48 kHz with peak data rates up to a maximum of 18,000 kbps for high sampling rate multichannel content.
I have plenty of ripped media and use Plex which is convenient but doesn't do ATMOS, I also use a 2012 Popcorn Hour Media Player for my ripped media and ISO files which does ATMOS but not 4K. Plex doesn't play ISO at all and the OPPO doesn't play ISO over the network. So what I guess I am getting at is that no one media player/app does everything and does it well.
All my physical media has digital certificates for VUDU or MoviesAynwhere. On VUDU these are broadcast in ATMOS and 4K, although I don't think the picture comes close to physical media in appearance, although close.. So, there are many different ways to watch a movie, I'll keep buying physical media where 4K/ATMOS/DTS is concerned, maybe at one point I will buy direct from VUDU or MoviesAynwhere for my media, but not yet.