A lot of people don't get why these changes are good or are misinterpreting them as nerfs or knee-jerk removals after a sudden appearance in pro play. Truth is, its almost entirely buffs, either in flat power or in usability.
But there's a reason - a few in fact - that these are well received by Garen players.
I'd like to start on the thing I see most repeated; that Garen is having defense nerfed for damage. No; he is losing 20 of his defensive farm stars because his passive is being buffed quite enormously. His up front defense has been shifted to superior sustain and lastability, because its more visible and more satisfying. He will be the same if not better into ranged matchups because of his better lastability.
Speaking of his damage, the reason its going up is quite simple; Garen's damage sucks. With a large part of his damage being tied to Villainy and an isolation mechanic that nobody really notices or cares about, removing it means that his general damage is going to go up. This is not damage creep; it's normalization and rational changes. It makes perfect sense that a champion who has his damage entirely limited to melee range scraps with no hard CC to lock you down in that range should have frightening damage when he gets you in that range. You can say whatever you like about that, but that's just how it is.
Another big and under stated reason these changes are excellent is because they give Garen *synergy*. The way his E works now (applying onhit, scaling off of AS) actually *opens* more bot lane combos than Yuumi where Garen is the carry as he is meant to be, because supports can now actually contribute to raising his damage threat as enchanters are supposed to do for their carries. Lulu with Ardent stacking buffs onto a Garen is a very scary thing, and this alongside his passive changes are likely two enormous boosts to his high elo viability in any lane.
I think my only concern here is that there's too little consideration for low ELO in these changes. I don't care about it, and I don't think riot should either, but Riot does, and none of these changes have moved his skill expression around at all; he's still very low floor and with how volatile a champion like him can be at low rank play, I think he might be too strong with these buffs.