Were you using full vision on the replay?
..cause..that can make pretty much everyone but the pros look derp.
Like- OMG WHY WOULD HE GO INTO THAT BRUSH? It was 'obvious' 3 of them were in there.
But, no, it's not obvious, you're just using full vision hacks. Try watching more golds, but only use 1 side vision. Or better yet, 1 side vision and only follow 1 guy, it makes it a lot more tunneled (and a lot more like your own games) and much harder to see their 'obvious' mistakes.
And even 1 side vision, following 1 guy, still have to keep in mind that you, as the spectator, don't have to worry about a lot of details, like cs'ing and gold and mana management and cooldowns. So you can spend the whole game thinking about map control and action choices, while they have to focus more on their person stat details.
And I think the main difference between bronze and gold is minor mechanical skills, not map control or decision making. And probably a slight amount better at teamwork/going with the flow.
(EG: you know getting dragon right now is 100% better than pushing mid, but 3/4 of your team mates push mid, now pushing mid with 4 or 5 is 100% better than trying to solo dragon while 3 push mid.
Bronzie jungler think- NO, MUST KILL DRAGON, DRAGON BETTER...and...die to enemy jungler and enemy jungler gets dragon, while team mates also die from overextending mid 3 vs 4.
Gold jungler think- DAMNIT DRAGON BETTER....but team is pushing mid so I have to follow them so we at least won't get aced from fighting split up, and end up with 3 of your team dying for killing 2 of theirs, bad, but not as bad as the bronzie outcome)
TL;DR- Gold is probably 10% better at landing/dodging skillshots, playing vs people who are also 8-12% better at landing skillshots, so, as a spectator, it doesn't look much different than your own games, especially if you're not limited by fog of war while spectating.