One of the best things about Halo: Infinite for me is that they returned to the series' old art style, to a large extent.
The reason why the Halo 4/5 Spartan armor designs don't work is because they violate the series' established shape language.
The very first game set down the rules. The UNSC are green and square.
The Covenant are round/triangular and purple.
Forerunner shit has dull gray metal with blue accents and trapezoidal shapes, and the Flood are pus-colored and organic.
The GEN2 MJOLNIR armors used shapes that were basically reserved for the Covenant. Lots of roundy shit. Lots of triangles.
It takes only a few moments for you to recognize this as a SPARTAN-IV, but that's because you have the advantage of seeing color and texture.
Watch this:
Which one is more instantly recognizable as a Spartan? Which one looks more generic, like they could be from any series? Let's try that one more time. This is what your brain sees when you see an S-IV and an S-II side-by-side:
That's interesting. 343i's Spartan armor in Halo 4/5 is constructed out of circles and triangles (like Covenant stuff), while the old Bungie Spartan armor is made up largely of rectangles and trapezoids.
The distinctive element of the MJOLNIR armor is the motocross-style helmet. It's the one part of the silhouette that immediately draws the eyes and defines the character. When you see a super-soldier with a helmet with a large visor and overhanging peak, you immediately think "that's a Spartan". The visuals do all the talking, instantly.
Back in the day, most Spartan helmets had this motif, hence they were instantly recognizable:
In Halo 4/5, a majority of GEN2 MJOLNIR helmets had a round silhouette and a tiny slit for a visor, or no visor at all, damn near resembling the visorless helmets of Blacklight: Retribution.
Now, along comes Halo: Infinite.
Oh wow, look at that. They went back to the old shape language. Your first impression is probably that this looks "better", but you can't exactly put your finger on why. It's all in the silhouette. Literally.
The rectangles are back. That's literally all it took.