theres less snowballing because towers were made stronger earlier and given better targeting. this leads to less towerdives, gone are the days where a rammus, maokai, seju with just a chainvest would towerdive gank you at level 4~5. even lee sin master towerdiver does it less and less these days.
so when behind its easier to towerfarm.
by no means was snowballing made more difficult in a 1v1 setting, we have thunderlords and extra % damage increases now than before. its so imperative not to die once in any lane without coming back gimped.
so thats what has shifted, instead of dueling it out and you being 7/8 after lane from constantly brawling and killing eachother you now get 2-0 were screwed now moments. any gold lead has much more of an impact now than it did in previous seasons.
back in the old days if you had a lead and bought a large rod, had 2 items you had a great big lead and huge dominance, but as soon as your enemy laner got their first item too they had kill pressure now as well, even though you had a whole item advantage you could still die in a 1v1 against him. so that meant skillful players won.
now we have item nerfs across the board and you need more items to successfully duel, so having an item advantage is more impactul.
people are more hesitant to go in and duke it out knowing if it isn't assured its not worth it.
look at LCS games, 0-0 24mins in. gone are the days of level 1 invades and 5v5.
riots been favoring laning phase and making solid leads at assuring who comes out ahead will have a strong impact on the rest of the game.