A new car might have blue tooth, a navigation system, and a rear camera, but you don't need any of that to drive and a ten year old car that's free is hard to beat.
Do you have a "problem" w/ blue-tooth, navigation, or rear-camera ???
I don't have a "problem" with them, for someone just learning to drive they are unnecessary.
The question/issue here is spending the SAME MONEY ($600+) for a lens for a 10-yo camera, (w/ none of the above), or the SAME MONEY for a camera w/ all the above.
It was the best-camera on the market 10-years ago when introduced, (using 60+yo "mirror" technology). I recommended it to many people at that time.
and a great tool to learn on.
But (any) Mirror-Less can be better than (any) dSLR to "learn" on. Do you have a problem w/ a direct-visual-feedback when making exposure/WB adjustments/corrections ???
It has excellent external controls that minimize the need to dive into menus.
I agree with that, but the same can apply to many ML. The same can apply to FZ, (or even RX), if all you want to do is "basic" stuff.
QUESTION for you ... w/ D300 can you adjust "A", "SS", and "EC" w/ ONE FINGER w/out removing your eye from the viewfinder ... (and no menu) ???
Nope 2 fingers - you got me. Can you put a 150-600mm on your fz1000 then switch to an ultrawide for landscapes?
You can w/ FZ. ONE "thumb" wheel can immediately do whatever needed w/out taking your eye away.
I agree, (FZ/RX is 20mpx but 12 is "enough").
Same with FZ/RX ... I have shot weddings, (and many other events), with it.
so you can learn and grow with it for years.
NOT REALLY, it is a 10yo camera, with NONE of the more current features, (that even dSLR's now have).
Very, Very, Very LIMITED, (does not even have LV or video).
Who cares about video? It is a stills camera. That's like saying a 10 year old corvette can't haul lumber.
It certainly does not even begin to compare with the "growth" to use unique features the FZ/RX, (or virtually ANY "ML" does today).
The bottom line is that the D300 was SOTA 10years ago, but you could not "give" me one today, (especially if I had to spend $600 for only "one" lens when I can get a much better complete camera w/ modern features FOR THE SAME MONEY).
The issue is that you seem to think that you have a magic solution that everyone should adopt. In other posts you made it sound like it was a miracle if you got a good exposure on a DSLR. The rest of us have no trouble nailing exposure, focus, DoF, or any other aspect of photography with our DSLRs. It just seems like the fz1000 is perfect for YOU - which is great - but you assume it's perfect for everyone. You have to realize that other people have different needs, wants, or shooting styles.
As time moves on, how do you upgrade from a fz1000? I guess you have to sell it and buy a whole new camera. How would the OP upgrade from a D300? Just keep that FREE camera as a backup and put any lenses he's purchased on a new body. Then he has two bodies that accept the same lenses.
It's obvious from this and many other threads that any further discussion is pointless. We get it. The fz1000 is the best camera ever and no one needs anything else. The sad thing is that beginners come here for help and you take over the thread. The OP has probably given up by now.