Hard disagree but go off and tell us why it's mediocre.
The basic easy common ones are the worse character designs and flat voice line delivery at characters that are literally about to burn up to death and occasional worse lines chosen. No need to dive into the marvel delivery versus b movie/old star wars delivery, its very obvious which is more memorable and has more charm.
The more intricate ones are the lighting, sound effects and feedback. The feedback from shooting most bosses is so poor that its hard to tell if you are hitting anything, the same can be said for when you the player are being hit. I died like 3 times in the beginning because I literally didn't know something was hitting me and had to start eyeballing my life bar like its a fighting game (same for the boss health bar) you never need to do this in the original. The sound effects are also tinny and muted compared to the original, they fall flat, sound generic and lack any juice. Explosions aren't cool and they do a bad job of providing player feedback which affects the game design. While the graphics are pretty alot of the lighting does a terrible job of making sure that enemies are visible. The visibility is often terrible. They didn't make the extra effort to make sure the colors they chose in the background contrasted well against enemies. This can tie back into that poor feedback thing.
Other ones that are important but smaller are things like tone, mischaracterization, or the title screen/intro/ending cinematic. The tone of scenes is often off, things that are supposed to be dramatic fail to land due to a lack of seriousness coming from the Star fox team about the situation they are in, this ties into the poor line deliveries from enemies caring about death. One of the worst tonal shifts was at the end with James, it falls so flat without Fox's impending death and the hoakey heaven music they put in (not to mention how braindead easy it is to follow him now cuts the tension in half). The mischaracterization comes alot from Fox being too similar to Falco. They try to tune up Falco to make up for this but it just doesn't work. Fox instead of being serious about taking on the mission to defeat the man that killed his father is more interested in credits and showing off. Fox is confident sure but he was always meant to be level headed and show why he is the leader. They turned him into Starlord (there are a ton of marvel esk tones in the remake).
The title screen is now a simple button press and not the incredibly dramatic introduction with the excellent title screen music, the intro cinematic feels less heavy than the serious star wars title crawl read because the characters in the cinematic don't seem to take it that seriously that they are about to die, sadly it the title crawl leaving things more up to the imagination is more effective here. Then there is the ending cinematic where they cut out the running in the fields from the Starfox crew as the great fox rises. That scene is iconic and its replaced with them just doing nothing in the arwings and a generic credits crawl.
Also really dislike the direction they gave for Leon where he was intimidating in the original in this one he sounds like weasel. Rob64 sounds weirdly pathetic also. The last main thing that bothered me is the generic mechanical aesthetic given to Andross and the bioweapons. The original made them feel unique and alien which added to the horror, the new versions look super typical when it comes to cybernetics. Andross's brain form is way less intimidating due to it not just being this gross horrific floating brain (another failure in art design.) Control wise I really wish I had the option to treat the right stick as a C stick like how I play with my Gamecube controller on the Wii Virtual console version (best version). The d pad being where things get used feels a bit cramped.
Also I totally ran into a freaking audio bug on Zoness in my 1st run.... The audio for 2 lines and music cut out and cut back in That shit never happened in the OG lol.
The only improvements are the cool little logs you can unlock that normally were in the strategy guides of the game, the idea of a challenge mode and I do like the concept of these cutscenes in between missions. Some of the music arrangements aren't bad but none has hit me that hard either. Oh and I think Katt's characterization might be an improvement too (even though she should be more pink in her art design). Also I appreciate that Wolfs voice is more inline with Assault (deep voice mercenary > British star wars villain) and I do think the portrayal/characterization of Pigma and Andrew are an improvement.
I wont call it bad because Star Fox 64s core level design is still underneath but it is very much inferior to the OG.