It may sound ridiculously obvious, but I think it's often a matter of being able to empathise with whoever you need to convince. Most organisations are in it to make money, and different people are different pieces of the puzzle of achieving that. If you can express the upside of the technology shift in terms relevant to, say, business developers or managers, things get easier. Whether you have closures or not doesn't matter, but time to market, time spent on bug fix releases instead of feature releases, etc do. Also, it will probably serve you best to thoroughly and honestly present both pros and cons. There's almost always cons (training, toolchain or workflow changes, building competence, talent availability, unclear longevity of technology being switched to) so if you're not upfront with the cons, people will wonder what they are and not knowing is scary, risking a higher susceptibility to scepticism. Also, if it's possible to use the new tech for a small project and you can show the upside with clear metrics, actions speak louder than words. My two cents.