This question has always come up while I'm learning new music. How many pieces do pianists learn every year? I've seen recordings of great pianists like Vladimir Ashkenazy who has recorded

All Chopin
Rachmaninoff solo and concerti
Shostakovich P&F Op87
All Beethoven sonata and concerti
All Mozart concerti
all Scriabin sonata
Liszt Transcendental Etudes

And much much more.

Then there's Jeno Jando who's got
All Mozart sonata and concerti
All Haydn, Beethoven, Schubert Sonata
Liszt Hungarian Rhapsody, transcendental etudes, sonata, years of pilgrimage
Bartok
Rachmaninoff

While I'm here struggling to learn these pieces, pianists like Ashkenazy among the other greats, knock these pieces out of the park.
All I have is

Chopin 4 Scherzi, 4 Ballades, Fantaisie Op49, 3 Etudes
Scriabin 12 Etudes Op8 (close to finishing), Sonata no2
Liszt Transcendental Etudes (getting 6,7,8,11), 6 Paganini Etudes, 6 Consolations, Nocturne in Ab, Ballades, sonata
Mozart Sonata K330,332
Then there's the random stuff like a few Debussy Preludes, Burgmuller op100

It's not a big accomplishment at 27 years of age. I've seen people at this age have twice this amount of pieces in their repertoire.

Is there a way to accumulate a massive piano repertoire in a period of the next 10 years?

The difference between the professional pianist and the other great amateurs, IMO, is their power of assimilation. There are many anecdotal stories of the greats learning works with the barest of efforts. This is no different than the great actors who learn Shakespear quickly and easily.

Concert pianists have time to learn massive amounts of music, mainly because that is their profession. For us amateurs, that is not the case. I work a lot, sometimes up to 12 hours a day. I can therefore only learn a new piece once every two months or so. It also depends on how difficult the pieces you are trying to learn are. You could learn 5 Bach inventions a lot faster than you could 5 Chopin etudes.