Fission devices have been very well understood since the early 1950s, but fusion reactions are somewhat less so. The NIF provides an instrument for probing the plasma densities and temperatures that occur inside a nuclear fireball, so is directly relevant to H-bomb research.
This becomes trivially obvious when you realize that a laser implosion fusion reactor producing power would need to achieve in excess of ten ignitions per second to produce the sort of power output needed just to power its own lasers ... and that each hohlraum costs on the order of a third of a million dollars. (What kind of power plant costs $11Bn per hour to operate?) Answer: it's not a remotely practical design for generating electricity, so it must be something else, and promoting it as "clean energy from fusion power" is a cynical propaganda move to disguise a nuclear weapons research tool.
The final clue is that the NIF is operated by Lawrence Livermore National Laboratory, whose primary job is designing and ensuring the reliability of nuclear weapons.
Indeed, the brute-force approach is to simply detonate a hydrogen bomb underground, tap off steam, then repeat. That was seriously investigated (I believe as part of Project Plowshare https://en.wikipedia.org/wiki/Project_Plowshare ), but the high cost of the bombs made it uncompetitive with other methods.
We have know for centuries that all you need to go high is a big fire pointing down, but soon realized that the hard part was maintaining the fire long enough to reach orbit or other planets.
And even when that would become possible, the problem of how to land in the destination, build shelters and grow food remains.
So, why we insist on this irrational pursuit?
First because we can.
Second because the the search needed to achieve that generates far more societal benefit than just the space goals.
And third because society can pursuit many goals at once. We have several people, just let them explore.
So, fusion is hard, but very probably not impossible. The pursuit of it will advance science and technology. If successful, can trigger societal changes we can only imagine today (serious carbon capture becomes possible. Smelting of very energy intensive alloys becomes cheaper and possible).
And if the ultimate goal of a miniaturized reactor becomes possible, our spaceships can fly basically anywhere.
This is where we are at, that is what we are aiming for.
ED: By now I assume I would be ignored if I was wrong.