My very 1st post in POTN was on 28-300L thread - after seeing far too many bad commends, which were from those people doesn't even use this lens before. I'm not very skillful photographer, and I'm only doing for fun - but my 28-300L can produce lots wonderful shoots, and most from my travel photography.
Sure, 27-70 & 70-200 are 'sharper' and 'better colour' than 28-300L; but my 24L, 85L and 200L primes can do 'better' than those two zoom; so we just have no ending debating for nothing.
Canon 5D3 + Zoom (EF 17-40L, 24-105L & 28-300L, 100-400L II) & Prime (24L II, 85L II, 100L, 135L & 200 f/2.8L II; Zeiss 1,4/35)
Sony α7r + Zeiss 1,8/55 FE
Nikon Coolpix A; Nikon F3 & F100 + Zeiss 1,4/50