If you are always a naysayer you will be right 90% of the time and can feel smug and pat yourself on the back for it (so, like everyone here). However, progress comes from people willing to take risks and make wild bets for the small chance that they are in the 10%.
In fusion research, pessimism is realism. Especially in laser powered fusion.
This experiment is producing 2.5 MJ of output for 500 MJ of input.
Roughly once a day.
After decades of basic research.
It's a scientific breakthrough in the sense that the rocks are now being banged together hard enough to make sparks. And a little more is known about rock banging than was known ten years ago.
But it's clearly not going to be producing power on a commercial scale any time soon.
Aside from the particular percentages I don't exactly disagree with your observation about the odds of being right or wrong in the respective cases, but I think the skepticism being due to an lazy pursuit of this smugness and self-congratulation you describe is almost entirely flawed as an explanation of motivations.
Instead, I'd like to suggest, in addition to having with cumulative exposure developed a severe hype allergy, a lot of us are burnt with respect to that so-called progress. There's been a fair bit of outright corrupted delivery on the promise of new technology, not least IT, and many people here are savvy enough to see the costs of wrongheaded changes.
'Move fast or not, we don't care much, but back off breaking things we liked and leaving the rest of us picking up the shards.'
The problem is this might be true, but it will not always be true. The horse was probably better than the first cars for a while, but progress changed that.
Old computers perform better and use fewer resources? Have you used, say, a PC in the 90s? The fans were loud, the power usage constant and high, and the performance lacking by so many orders of magnitude that it can just be emulated in software today.
All the new stuff, however, has marketing and looks shiny.