I feel like people forget this manga was regularly a short read, many chapters being like 4 pages long sometimes.
Roughly 4 pages at 235 chapters means that less than 1000 pages of Annoying Senpai have been published.
Compare that to another average RomCom like Don't Tease me Nagatoro (also ending soon at chapter 154), which has 19 tankoban volumes currently of roughly 144 pages for more than 2500 pages and that's a low estimate.
Or Uzaki Wants to Hang Out, 111 chapters, 12 volumes, (still ongoing) for an estimate of almost 1800 pages.
This story has NOT taken as long as some of you people think.