So I think I figured out why laning against Garen feels so draining...
... he suffers from the "Riven Syndrome".
Usually ressourcless champs are gated by their cooldowns. So they shoot their skills and then you have a window of opportunity to strike - so the theory.
Both Riven and Garen have an essential core item that completly eliminates this weakness for them:
for Riven and
for Garen . Sure you get the BC a bit later as Garen than Riven can pick her item, but it has better stats, so it feels even more unfair. Also Garen also has sustain, making it impossible to bully him out of lane.
A Garen with a BC has usually 30% or even 35% CDR with runes and masteries and his cooldowns become kinda nonexistant - or at least they become so low that he can back off, wait for them, come back and not even miss one CS.
The moment garen has his item he will be unbeatable in his lane. Sure you can stall and waveclear, but there is nothing you can really do to actually beat him. For trading you would have to find a moment when his Q or E are down, but that rarely happens with all that cdr. And the little damage you do? Either blocked by W and quickly outsustained by the passive + hp reg. Not to mention the free tankyness. before Garen had to build tank items to get stats bonuses. Now he gets them for free. That alone wouldn't be a problem but combined with everything else...
Do you know how that feels? To know that unless this garen suddenly decides to troll or go afk there is no way you are going to get him out of lane? And that not because he is skilled (let's be honest here, garen is not a mechanically difficult champ), but simply because it's how his stats are by default. Sure, teamfights are a different story later but until then laning vs Garen is worse then going against a fed Riven.
No fun, zero interaction, and it just feels draining and unfair. Redo the rework please - Garen as a champ is so old, he needs more than just true damage strapped to his ult to become a healthy champion...
Tides of Blood
Flame spitter
20-button combo forcing auto-attacks for mark detonation
poking things down gradulally, his sustained-DPS ultimate
QQQ + AA AA AA
Spin to Win
Auto-attacking and nothing else
Mostly auto-attacking and nothing else
A lot of things that are basically auto-attacking (and hit hard by anti-AA items)
burning things to death, while auto-attacking them
Also burning things to death while auto-attacking them
have manaless AA bonuses, but mana-intensive burst skills.