Key stones - fulfil XXX battle conditions for extra power. Champions rise and fall depending on synergy with keystones, Keystones promote generalisations and they're flashy ( you can literally envision an LCS shoutcaster screaming about how Phase Rush has activated and XX is going to be impossibly hard to peel now or about whether YYY will land that 3rd ability/auto to proc electrocute)
Jungle Plants - gimmicky, again contributes to generalisation as now most every champion has access to a variety of gank paths or a cheeky dragon/baron steal, whereas such flexibility used to be limited to a select few mobile champions. (again, you can literally imagine a LCS shoutcaster screaming about whether XX will make it to the blast plant to survive or YYY will be able to use the blast cone for an objective steal/sneaky gank that shouldn't be accessibly to him in the first place)
RNG Dragons - HUGE gimmick. Games can literally be decided by which dragon spawns first. The dragons give generalist stats that interfere with the strengths/weaknesses of champions and AGAIN promotes what? You guessed it, generalisation.
First Blood Tower - Man, back when I used to peep at the LCS every now and again I remember casters screaming about who would get the first turret in a lane-swap like it was the best thing ever...I honestly wouldn't have a big problem with FB tower if not for the fact that, for some reason, Bot Lanes turret is the squishiest in the game.
Baron. Honestly, bring back the old baron. As of now Baron is simply a gimmick that is being utilised to cover for how imbalanced the game currently is. A lot of winning teams need it to end (because catch-up exp, increase of damage across the board and so on has actually made leads less impactful. With damage how it is when fed you quickly reach a point where you're simply 'over-killing' someone, while the excess of damage and catch-up exp means that people who shouldn't be a threat because of how you've denied them still are'. Or, a losing team gets it and is suddenly back in the game. Either way Baron essentially distorts team comp weaknesses (suddenly a team bad at sieging will be good at it, while a team with great anti-siege will become lack-luster.)
Baron was fine as it was. Dragon was fine as it was. The only improvement of the Keystone system is that its free and can be edited in champ select.
Jungle was healthier and more fun to play back in season 4-5. The current scuttle changes being discussed again reek of a gimmick that will simply give some LCS shoutcaster a lot to scream about.
This is my opinion.
I'm also of the opinion that the game should be reverted back to season 4-5, though, so take what I say with a grain of salt I guess?
I'd like to see other peoples opinion on the matter, but personally I feel this game has gotten worse with each passing season.