On the one hand, it's totally understandable that these guys are in their mid-40s and have injuries / limitations.
On the other, Shamrock is a showman and has to realize that this drives his value way down. Had this match been exciting (in spite of being a grappling bout), it's entirely possible he could've had a life-after-death career competing against other big names (IE: his brother Ken, Royce, Sonnen, etc) under a far more safer and favourable ruleset, and still made some cheese.
But we'll see. Maybe this was just an isolated incident, and future grappling bouts won't be as boring.