Great improvement IMHO.
I suspect it is the same for most people. That's one reason why we have to try so hard to avoid even spacing and lines.
Even without a creek/path most forest settings will benefit from '2 peaks' - a dominant tree and a second tree. With deciduous canopy I prefer rounded, billowing canopy rather than rigid triangles but that's a few years off yet.
Larger, thicker trees in front help force perspective and makes the planting look way larger than it is. Known as 'close view'
Smaller trees in front is known as distant view but, IMHO, lacks depth because thickest trees in back does not compute with our knowledge of distance and perspective. However, you are welcome to design and grow bonsai that please you.
Smaller trees at each side already make the group look much wider than previous.
From original front, smaller rear trees give impression of greater depth, however stream is fighting that view. See below.
Narrower stream looks better but still appears relatively similar in width from front to back. I would double the width at the front and taper off to half current width at the rear. That should fool the brain into believing the stream is coming from way back and therefore make us see a much larger, deeper forest.
Should not be necessary for quite a few years. Roots are pruned as necessary to make space for new roots. Trunks will get thicker but the trees do not get further apart so the spread of the forest won't change significantly.