VST upgrades

Since MuseScore is open source, you're welcome to contribute.

You wrote:
...please put professional recorded orchestral instruments as standard sounding instruments.
and:
I just feel like there isn't a reason why a notation program can't have great sounding instruments.

MuseScore is constrained by the licensing requirements of any "professionally recorded" soundfonts. Such soundfonts cannot simply be bundled "as standard sounding instruments" within the MuseScore program, and then given away for free.
See:
https://musescore.org/en/handbook/3/soundfonts-and-sfz-files

You can search the internet for soundfonts which may be more to your liking (some may require purchase).
You can try one of these (free) orchestral soundfonts:
https://musescore.org/en/handbook/3/soundfonts-and-sfz-files#orchestral…
You can make your own soundfont. (Search Youtube videos for How to's)

Welcome aboard...

For the record, the default soundfont does features professional recorded orchestral instruments. Each individual note is a recording of the corresponding note. The problem is, real instruments playing an actual phrase don't do it with perfect copies of individual notes, there is a whole different thing that happens where notes are played back to back (eg, slurring) that you can't reproduce via simple MIDI playback regardless of how good the individual samples are. Similarly for other subtleties of performance. It's not a question of how well the instruments are sampled - it's about the AI needed to go beyond merely playing each note one at time but actually capturing all the nuances of the ways notes are combined.

That said, such AI is currently being worked on for MuseScore 4, see the discussions in the Announcements forum for more info.