There are two types of fusion: hot and cold.
Hot fusion is doable, and not even especially difficult, so long as you're comfortable dealing with temperatures in the millions of degrees. It might conceivably be used for power stations, but I think it's far to say no-one's ever going to put a hot fusion reactor in a car.
Cold fusion is, as of right now, unknown. There's no reason to assume it's impossible, but the only projects that have had even inconsistent results have turned out to be fatally flawed. It's possible that the vital breakthrough will be made next week, and small, highly efficient power plants will be being mass-produced within a decade, but it's not exactly the way to bet.
The JET reactor you mention is a Tokamak fusion reactor which started running in 1985, making it the second oldest Tokamak still running. It weighs five tonnes, runs at a temperature of 100,000,000°C and generated a peak current of a whopping 16 megawatts for a little under a second. For comparison, the nearby Didcot A power station generates a sustained output of 2 gigawatts. ITER will be several times larger than JET, and is planned to output as much as 200 megawatts for up to five minutes.
In thirty or forty years, we might have a hot fusion reactor that can be used in place of a fossil fuel power plant, generating a serious amount of energy, but right now we have 5th generation fission reactors that are safe, clean and efficient. But people remember a 1st generation plant with almost no safety features (even by 1st generation standards), crewed by people who'd never been trained on a nuclear reactor who decided to run an incredibly dangerous test during a shift change without telling the workers, and they declare that any new nuclear power station is a Chernobyl waiting to happen.
Personally, I think that demonising fission reactors is the biggest mistake the environmental movement ever made.
Oh, and ITER is no longer an acronym. The PR people thought that having both "thermonuclear" and "experimental" in the name was a bad idea. So now it's just the Latin word for "direction" or "journey".