To make a city sustainable, there needs to be laws and procedures set in place to make the environment, people, and animals who live there safe. One recommendation that we could do is encourage people to walk or bike short distances. This will lower Co2 emissions from cars and will save you gas money. There should also be community gardens for citizens to take part in growing food for themselves and the community. Community gardens are sustainable, good for the environment, and cuts down less forested land. People could also get paid to pick up plastic and other trash littered around the city, so it won't end up in the ocean or on an animal. Lastly, all buildings should be powered by renewable energy sources like solar panels or wind power!

There are some parts that aren't feasible to some countries and cities, but most of your points are valid. Cities are definitely starting to, or already are, encouraging carbon-neutral transportations, but some of those cities don't have the correct amenities to support that network, and you can't just place those bike lanes willy-nilly, people want their parking for their gas-guzzlers, and bike networks are distracting and may lower land value to the homeowners on said street. City planners need to find routes that are used, and may need to call mulligans, which cost time and money.
It is generally agreed that gas prices are getting higher and higher, discouraging drivers from driving, but still paying for the car running fuel. People are also not willing to take the jump for a gas car to an electric car, because they fear that they can't afford it. They are not willing to take the jump because they don't know the implications, whether it be good or bad, but it seems that (don't quote me on this) that getting an electric car actually saves you more money in the long run, but people are just too scared to make the jump over.
There aren't many criticisms against community gardens, (that I know of) but they can't rival the amount of food produced at a farm. I said in an earlier post that unless you develop a way to grow vast sums of food in a small space consistently and for a low price, we still need to stick to importing/eating farm grown foods.
Picking up trash from city properties are definitely good things, but most people don't want to handle trash, and depending on how much you pay. Most people already have day jobs that probably pay more, which leaves the weekends. Then again, earning some extra bucks over the weekend is good, but they want the weekends off, not doing work. Also, where will the money come from?
Renewable energy is good, but they are still expensive compared to building up an oil or coal power plant and burning it for energy. The reason developing countries burn fuels is because that they don't have the funding to construct these renewable sources, not to mention other amenities like housing and water, so unless we give them the funding and the parts, they'll keep burning things up until the have a stable and growing economy.