Recording into computer audio quality issue

[DANDİNİ]

I was trying my XV-5050 with the new setup. I constantly plug, unplug to/from mixer-sound card etc. I used my module without touching a knob for 15 years. But now i tried reaching banks and presets from another midi controller, without pc.
What i noticed during my try-outs was, I was so impressed by the quality, it's because I've used XV's phone out only. And as i said last 15 years i set "seq template" and get the presets, banks from Sonar. But now i dial the value knob and i though it's because i am into patch mode and sounds are so beautiful.

But no, when i connect to my mixer, the old low quality came back. Less inspiring, like i don't know how to describe fogy? Anyway i think you get what i am saying. Directly from phone out sounds are crystal clear. I hear way better bass and i hear like just next to you. Because i get used to quality after few weeks of phone out and suddenly go back to mixer I first thought cable jack didn't really sit.Yes, that was my first impression.

I removed mixer, connected to my sound interface let's say quality has 20% increased.
Mixer Mackie Onyx 1220 i followed what the manual suggest for the computer oriented scheme
Focusrite Scarlett 18i8 2nd gen usb
I couldn't sync optical and SPDIF. I am definitely sure its Scarlett's fault. I used to connect my module via optical cable years back

Is this very expensive interfaces overcome this issue, you think? RME, Motu stuff?