I problem is not the view controller length but putting code that does not belong in the view controller. Everything has a place and there is a place for everything. If you start creating separate components like Datasource, Dataproviders then your view controller will automatically become leaner.
I explained many of those approaches in my course “A Complete Guide to Lean Controllers in iOS” here. https://www.udemy.com/a-complete-guide-to-lean-controllers-in-ios/?couponCode=MAKEMELEAN