Probably, not every setup can reveal these differences and not everyone who hear will write about it here.
you have a nice system but there are plenty of people here with equal or better (more expensive) systems and there are plenty of posts from people in that past who have complained about sound degradation in the past. Don’t fall into the trap of thinking you are special…
Is this perceived reduction in sound quality just with Tidal or do you have local content as well? [edit: ok you mentioned flac content also so not just Tidal I presume].
Does the Tidal app sound better when playing Tidal content?
two friends of mine that I trust their opinion, agreed with me. They heard degradation on their, different, setups as well.
Both of whom also don’t take backups of their system either I presume!
Do you not have the .exe that you used to install Roon core in the first place? If so, uninstall Roon core and reinstall from the original (older) .exe
Basically unless a bunch of people come out of hiding to agree with you, this thread will go nowhere, especially as you are playing MQA content for which many people have “divided opinions”.