Wall of text incoming.
tl;dr - Dota is more skill intensive, punishing and things aren't granted but need to be earned.
First, I disagree on toxicity of community. What I've actually seen so far, LoL has a way bigger problem with "decline of civility" than DotA. Mainly because playerbase is younger. As for popularity, DotA did lose quite many players in this Dota -> Dota 2 transition, while new players hopped onto LoL-train. Old DotA players seem to be getting back, though, me included. I do not follow LoL pro scene, but I DotA one is very, very active.
Steeper learning curve is true, but, I don't see that as only a bad thing.
First, LoL has way more grinding outside the game. You can't play any hero unless you pay, same goes for runes and Masteries - as a noob, you are, for some reason, already handicapped going after a more veteran player, just a game start. But, once you get most of hte things unlocked, it vanishes. Still, I don't see why Masteries and runes need to be grinded for.
But, more importantly, it's the game itself. To me, sometimes it's like DnD 3.5 vs 4.0. DotA is way more punishing, and LoL has too many things given for granted. Also, I do think DotA is more skill intensive.
Like, in LoL, every hero has a access to Flash ("Blink" in DotA) - which is almost always taken - and another skill, whichever you think fits the best and fixes one of your weaknesses usually (also runes). Plus, many more heroes actually have inherit flashlike abilities, and couples with brushes - getting in and out seem much easier and is kinda taken for granted.
In DotA you can get any hero a Blink Dagger which costs resources and inventory space. It makes it a way more fearful and unique ability when you really need to work for it and not everybody can access it easily.
It is like that with many other stuff, this is an example that irks me the most.
Mana management is a breeze in LoL. The sheer relation between spell cost and amount of mana is MUCH, much tighter in DotA (for example, most Strenght heroes cannot cast more than 1 or 2 spells without depleting their mana pool) - again, this makes using your abilities only when needed and not wasting then a skill that is much more valued in DotA. Too many heroes take it for granted and can just spam spells with little consequence (some don't even use mana at all).
Dying is punished harder, as you lose gold in progress. It might be a bad thing, might be a good.
Laning is, I believe, harder. You actually need to deny your own creeps, I am not sure but last hitting seems a bit harder (or maybe I'm just bad at it) and generally it is much more easier to keep a lane given the surplus mana and also free abilities that save your butt.
I am not completely sure on LoL items, I know that DotA actually has a lot of activated ones - .which, to extend, make up for "Masteries" and actually need to be worked for. I think LoL's are mostly passive. I did dislike this creep of activated items that happened, but I do support it now.
I am not too thrilled about their skill system either, I didn't play much so I don't know heroes too well, but I believe there are too many slows, blinks and nukes among heroes - and many heroes that wouldn't get such abilities in DotA - do. Also, there are some skills that certain heroes have in DotA that they lack in LoL (creep conversion/sacrificing, for example) and usually I like DotA's choices better when it comes down to it. Not that all of LoLs are terrible, they have a fair share of great/unique ones that DotA perhaps misses (though, they aren't adding any till they convert the whole DotA 1 to new engine first).
Generally, there are many more things to manage in DotA, making it harder, but way more rewarding.
The thing that I dislike about DotA 2 the most is that, out of legacy reasons, they retained too many of WC3 engine quirks that make DotA work unintitively sometimes. I.E. too many spells or abilities break some game rules, most about what can go through magic resistance, magic immunity, armor, damage reduction and so on. There are too many of these "Well, it works like that, but this skill and that skill still circumvent that and work differently in a small, but sometimes very relevant way."