The Beatles also introduced more complex harmonic progressions to the pop rock world. Songs with many chords instead of just 3 or 4. Just think of the "minor four" chord for example. Sure these harmonies hard been around in Classical and Jazz styles, but not so much in pop. And they sang harmonies in those complex chordal structures.
The fact that they wrote, recorded, and sang their own songs was a fairly new approach in pop music.
The guys had very strong distinctive personalities, that combined in a synergetic way, that surpassed their individual talents.
New Instrumentation was another innovation, string sections, sitar & tablas, mellotron, layers of electric and acoustic guitars, horn sections and soloists, etc... hadn't really been exploited in such a fresh way before.
Then there's the first real use of extreme stereo panning... listen to Revolver for instance.
The lyrics & subject material were breaking down barriers, alluding to sex & drugs in a fairly open way.
The haircuts, fashions, costumes, new cultural & social ideas, the music video, extensive music films, the list goes on and on and on and on, etc...... and we've just touched on the tip of the iceberg...
I remember saving my money as a teen, just so I could buy the new Beatles record on the day it came out.
These guys and the machine behind them broke the mold of the past, and set a new standard that is still in place 40 years later.
Your question is like asking "what's the big deal with Ford or Mercedes" in the automotive world... they defined the concept.