It's a mixed bag…
A lot of my local national forest and wilderness areas burned in a series of fires over the last 5 or 6 years.
I recall one particularly good example of hiking in an area after a fire…
A couple of months after the Zaca Fire burned through most of the San Rafael Wilderness, I did a ~40 mile mostly on-trail loop with a friend to suss out the damage and take advantage of the incinerated brush to explore off-trail areas along the way and search for previously unknown native american rock art sites, etc.
The thinner brush was great for getting off trail and being able to reach previously unknown or inaccessible outcroppings and caves. We found some sites with evidence of Native American occupation/use that were new to us. In that respect, the fire provided a unique opportunity to explore some new areas in a much more efficient manner.
On the other hand, the landscape was sparse and looked like the moon. Ash clouds would get kicked up with each step as we walked. Camps and landmark trees were obliterated and basically vanished other than a few metal signs and ice box stoves. The trails were completely gone in areas where heavy rains in the months following the fire washed away all the top soil. Swimming holes were gone; filled in with soot/debris. Creeks and streams were also significantly reduced in capacity. Wildlife sightings were down to nothing.
We bushwhacked along, fighting the charred skeletons of brush for mile after mile. Weaving through the charred remains of chaparral and stepping over endless tree falls is really slow going. By the end of the trip, we were quite the sight… Scratched arms and legs, torn clothing and packs, covered in soot, and to top it off, I got a bloody nose after a particularly stubborn branch snapped back and hit me square across the face, so I also had blood splattered all down the front of me. We looked, and felt, like we had just battled our way through one hell of a challenging hike.
And yet, I'm sure after the next fire(s), I'll be back out there again capitalizing on the opportunity to explore areas previously hidden by decades of brush.
Oh, and I don't know if this would grow where you hike, but watch out for Poodle Dog Bush. It's a particularly nasty CA native plant that grows in burn areas; it's typically found from the southern Sierra south to Baja. It gives a rash similar to poison oak. No bueno.