Well, about the third world countries I do know about the issues on a more global level, but if we're gonna talk really locally as per why there is no drinking water at all, I must tell you my knowledge ends there. :) I only know what some european aid organizations report regarding the issues, like corruption, low knowledge, little amount of schools etc.

Solar technology is very rapidly improving, but it is nót sufficient right now to replace the technologies (e.g. fossil fuel) we are using currently. Let me show you this citation: '' solar energy has immense potential and could emerge as a major
source of energy, in particular if energy-related carbon dioxide emissions must be reduced to quite low levels and if other low-carbon technology options cannot deliver on large scale. While this outcome is hypothetical, it does suggest that current efforts are warranted to enrich the portfolio of clean and sustainable energy options for the future. '', written by Maria van der Hoeven. (CEO of International Energy Agency).
Or from Apple's HQ building, entirely out of solar panels: '' Clearly, this won’t be enough power to power all of Apple’s HQ operations, but as Steve Jobs mentioned in his case to the Cupertino City council, Apple will be able to generate a lot of its own power and will run from an on-site power facility with the normal grid used as a backup.''
source: https://855casolar.com/around-5mw-apple-headquarters-solar-roof-make-among-biggest-us/

I agree completely about the shitty quality product industries produce these days however, back in the day everything was made more robust /sturdy. Phones these days can't even live longer than 3 years :') But it's definitely not a simple problem to solve, because if it is, why hasn't it been solved then?