If you start to think of 'temperature' of individual particles as 'speed with which they move' that is a useful rough approximation of trying to figure out what it means that something has a particular temperature. Containing the plasma is hard not just because of the temperature it is at but simply because it tends to destroy anything that contains it and that doesn't really change all that much for 15 million degrees Celsius, 30, 100 or 150. What it does change is that at 150 million degrees Celsius you have some hope of extracting useful work from a very small quantity of plasma. If you don't get it up to those temperatures - again, as far as I understand it - then you will always be putting in more energy than you are gaining because of some fundamental physics limitations.

So the smaller you make your reactor the hotter you'll have to make it to make it net positive. This leads to the counter intuitive result that making a much larger reactor is actually quite possibly easier than making a really small one. The rate of heat loss is much smaller for a larger reactor and so it becomes easier to sustain the reaction and to extract useful energy from it.

It is very well possible that none of the reactors currently on the drawing board and under construction are going to be working well enough to give us a sustained reaction resulting in net yield. But we're getting closer and closer to that and there is some (small) chance that I will still see this in my lifetime.

The catch is that as long as you can't get a small reactor to work getting funding for a much larger one (which you actually may be able to get to work) is going to be extremely difficult. We like to see proof before we scale up. In this case it may well be that such small scale proof can't be done or can't be done in a way that it it will convince backers that a larger scale device will work.