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.
While you might be technically correct, what people mean is that 90% of the work was focused on either random status quo stuff or other couples. Then, out of nowhere, where people expected it would need another 200 chapters to develop the actual main pair, the author just 0-100MPHs the whole plot, and now he cuts it all off entirely.
I think most people would gladly give up 10, 20, 50, 100 chapters of whatever non-important stuff he spent his time on for an inkling of a decent story here.
So, no, this work took a very long time, and it absolutely waster all of it for a whimper kind of ending.
As a reminder, we still practically know nothing about Takeda-senpai, fuck, we don't even know what he thinks, truly, of Futaba.
As others have said, he went from a shallow character to a literal plot device.