Soooooo many of these HAVE been invented just various political issues are preventing them from being properly developed/implemented.
"Reliable, pollution free, renewable energy source. That's also cheap." There's several but 'big oil' put pressure on those who could invest/implement so it never really comes to fruition. We need politicians - worldwide - who aren't beholden to 'big oil' in any way.
"Traffic lights that can read sensors/transmitters in the vehicle so that they can be "smart" and change according to traffic volumes." As pp has said already exists just not prevalent yet.
"A completely waterproof mobile phone with a shatter/crack proof screen." Already exist or certainly could but would make them last longer & not need replacing/repaired as much which I suspect is where mobile phone companies make a lot of their money.
"also, another form of contraception that is 100% effective, is not intrusive (ie coil) and does not make you bleed erratically (ie implant, injection) (in an ideal world, no bleeding at all please!)" I take noriday back to back so no bleeding with Drs support BUT it's taken over 30 years to get the support! There's no medical reason for bleeding being necessary but...patriarchy, medical sexism...
"A toaster that actually fits in slices of bread fully. I shouldn’t have to stand around turning the bread whilst using something that was designed for convenience." There was a thread on this recently (yours?) that I almost replied to then dropped phone & lost it. Many toasters (even my £5 one) WILL take the full slice if it's put in the toaster landscape orientation rather than portrait.
"A contraceptive pill for men" again, already invented, didn't make it past first stage of human trials because the men couldn't WOULDN'T cope with the MINOR side effects (which were the same as those BILLIONS of women out up with and are EXPECTED to tolerate)...again patriarchy and medical sexism
"A shower that also dries. I hate getting out the shower wet in the winter." Again, already exists, my friend has one... But currently £££££ you turn shower off, hit a button and get blasted with warm air like a body sized warm air hand dryer. Lovely.
Personally as an OCD sufferer I'd like a self cleaning home inc especially self emptying bins and self cleaning toilet! My most hated jobs.