Not likely. Assassination is rarely a viable strategy. It tends to recruit from those who admired the the one killed and create sympathy for their cause. You can't really scare people who aren't afraid of dying.
Assassination... is usually stupid for the reasons you assert.
And yet, removing trained, experienced, highly-skilled professionals from any field is widely recognized as a certain method of crippling that field.
Remove all the doctors from a hospital, and the internists will certainly step in to fill the void. But the hospital won't run nearly as well. The internists won't do as good a job. Less people will be treated. More people will die.
Remove all the Detectives from a Police Department, and have Beat Cops take their place. The Department's criminal investigations will suffer as a result, plus you'll have less cops on the beat. Maybe neighborhood vigilante groups will move in to fill the Beat Cop Gap, with predictably inferior results.
Remove all the professional soldiers from an all-volunteer army, and fill the ranks instead with green conscripts. The quality of your fighting force, and its chances of success on the battlefield will plummet, with disastrous and bloody consequences.
Fire all the executives in a company, and promote the receptionists and shipping/receiving staff to the corner offices and penthouse suites. See how long the company remains viable.
Kill a talented, experienced, well-connected insurgent leader, and his replacement may be equally as fanatical, but he will probably not be equally skilled in leading an insurgency. Instead of having the benefit of however many more months or years of mentoring from those more skilled than himself, he'll be forced to accept on-the-job training, in a job where not already being an expert is often a ticket to sudden death for you and the insurgents you're trying to lead.
How deep is the is the Taliban's leadership roster, anyway? How many expert insurgent commanders do they have sitting on the bench, like so many second- and third-string quarterbacks, just waiting for the starter to blow out a knee so they can get out on the field and show just how good they are? And how many of them, for all their eagerness, for all their game, are just not that good?
I'm not saying targeted assassination always works. I just don't see how "there's always gonna be a willing replacement" is a valid argument
against targeted assassination. Unless every Talibani in the tri-state area is equally well-qualified to command the respect and obedience of his peers, and equally skilled in the arts of managing an insurgency against a superior foe, it seems to me that forcing constant leadership replacements is bound to weaken the Taliban and make it easier to defeat.