I have the 12.9 iPP 2020 with MK and Apple pencil. Taking the thread title au pied de la lettre, my iPad Pro has completely replaced my laptop (MacBook Air), to the point where I no longer use the latter at all, but have given it to my kids to use as their school computer.
Has my iPP replaced Macs entirely? No. I still use a 27” iMac (2017). I’m an online teacher (Greek and Latin), and the Zoom desktop app has more capabilities than the iPad app. The ability to spread out lots of windows is crucial to my workflow: I will frequently have a Powerpoint or KeyNote slideshow that I’m showing my students, plus Zoom’s webcams, plus a PDF or ePub book, the Notes app, Photos app, a couple browser windows with course materials (quizzes, etc) in Canvas, and iTunes all open at the same time. It’s no problem on the 5k screen; it’s not possible on the iPad. Of course, wasn’t possible on the MacBook Air either. So the iPad has successfully replaced my laptop. I do all my class prep, reading, and grading on the iPad. It’s only the actual teaching that happens on the iMac.
My son has a 2019 MacBook Air. He is casting serious sidelong glances at my iPP. The screen is better, the processor is faster, it has twice as much storage as his laptop, to say nothing of its tablet-specific capabilities (pencil, portrait orientation, etc).