If you have problems explaining why features need their time, it's not about your frameworks, it's about explaining the clients in all honesty what happens. Or, if you want to get paid enough, you simply factor in some risks into your budget planning and up your budget. They don't have to know that you only needed 2h to get nearly everything up and running and 6h for that one sneaky feature. Use asymmetric information (https://en.wikipedia.org/wiki/Principal%E2%80%93agent_proble...) to your advantage. It's not about the toolset, it's about your mindset.