I've had a very low failure rate with the Libre 2 and more recently the Libre 2+. I have had one fail (after 2 days) and one come off in my sleep, and that was before I started wearing a stretchy 'armband' over it . The armband is breathable and comfortable and protects the sensor unlike other solutions involving extra patches, adhesives or 'sticky' wipes. For the two problems I had, Abbott were very quick to replace them for free.
I concede that there are a number of people for whom they won't work for whatever reason, and I've listed a number of possible reasons below. It may be a bit strong to say that as a product it's not fit for purpose when there isn't clinical evidence to support this assertion, all we have is anecdotal reports on a handful of user forums. If it doesn't work for you, perhaps work with Abbott to try and sort it or get your GP to prescribe a different brand? Good Luck!
Hope some of this may help those facing challenges with CGM sensors.