I agree things happen, but stating that having to uncock a glock or xd etc to remove the slide is a bad design is not a fair statement.
Almost anystriker fired weapon has to be cleared and or the striker returned to a neutral position before the slide is removed. Ruger uses an ejector swing down that renders this not needed. As well as the XDM that uses a disconnector attached to the takedown lever. The m&p uses a disconnect also but the process to take one of those apart is similar to the ruger.
Glock requires the trigger be pulled, slide pushed slightly rearward and tabs depressed.
XD slide to the rear, lock it, swing assembly lever up, release slide, pull trigger.
Even the 22\45 requires the trigger be pulled to disassemble it.
A fair number of striker and internal hammer weapons require this.
Now the design advantage the Glock and XD have over the Ruger and M&P is simplicity in the field. These two field strip to 4 major components with no additional small parts to loose and render the gun unusable. As I have stated before the Glock is a combat weapon. It is not the average Joe weapon. It was designed for a specific purpose in combat and law enforcement and civilians feel in love with it, but it is void of extra safety features and idiot proofing.
Yes stuff happened but it isn't poor design it is poor execution by the handler. I will make mistakes but will never expect the weapons design to prevent them.