Seriously, you can claim that you cant balance a game like LoL, but cmone, there are other games of the genre proving you can. DotA tournaments always have way more variety than LoL games... So its possible somehow.
TurquoiseYoshi5 votesTop: 
Jungle: 
Mid: 
ADC: 
Support: 
That's 31 off the top of my head. That's more than 20, so title is objectively incorrect.
GeminiRune2 votesAllow me to add to that. When you ban out a role with more than 4 champions or just outright confidence in pocket picks, you wind up with something along the lines of:
Top: 
Jungle: 
Mid: 
Bot: 
Support: 
That's another 22 for you.
Raoul1 votesNow look how many of them were actually picked more than one time, suddendly all the diversity is gone.
TurquoiseYoshi1 votesWell, if you discount the permabanned LB that I included because it was permabanned, that's 30.
Wow it's all of them.
Hyperiön1 votesUh Sir, gitgud. Move Camille to that support spot, because that is where it was played!
TurquoiseYoshi1 votesshit i've been xposd
Faie2 votesDotA has such high variety in comp play by throwing out balance in low level play. Every hero is balanced around competitive play, so you have heroes that have 30% - 60% winrates in your average silver games. You have to take a choice, would you rather the game be unfair for the community or for the pros?
oSEXYPLATYPUSo1 voteswhy would they play subpar champs or binary champs when other champs just do much more better?
and after the next patch you will see a shift and the champ pool that is being played
bye bye rengar and kha jungle
Raoul1 votesAnd that is the problem. We have so many champions that can just do everything that it would be stupid to pick one that is less good at everything than another one. RIOT has to basically rework every champion, giving them something they do very good and therefore create a pool where you actually have to choose how you want to play the game, and not where you have to pick or ban those who just rock at everything.
oSEXYPLATYPUSo1 voteswell back prior to season 5 we use to have "hard counters " in the game and im sure people bitched and cried over that (back when 
was ban/pick top lane meta in pro play ) so riot reworked, re balanced, re tooled, created new champs that have all in one kit and you just pick the best for the meta/patch
Raoul1 votesThis game NEVER had hard counters.
If you want to see how a hard counter workd, look at DotA. Renekton was ban/pick because he was, again, the best at everything at the time.
oSEXYPLATYPUSo1 votesno there use to be hard counters
Raoul1 votesName one...
Support Bοt1 votesPantheon vs Nidalee top. No matters how much you are trying to win as nidalee, Pantheon always win.
Nidalee vs Garen top. As above, nidalee always win.
Fizz vs Galio. Fizz has no chances due to his shield.
Handy Sandy 1 votesJust nerf all those mobile AD assassin/fighters and make tank hitboxes bigger with the more health they have so squishies can't abuse health items.
Problem solved.
xJLx MCHammer1 votesAll they have to do is impose a new rule "Champions played in this match up cannot be picked for the next two match"
That easily creates at least 30 champions pick per match up. They need to revert the 2 extra bans. It doesn't add too much strategy as many teams don't even utilize it. Not to mention, it just drags a pre-game. Feels like I'm watching Sunday football; 300 mins of talking and analyzing and then a game starts...
Lugg1 votesAmen
III BAKURYU III 1 votesLeague isn't Dota; League is better or Dota is better but the fact the matter is they're different. If Dota does something better than League go watch Dota.
These are pro players they play whats strong ATM, they won't play some garbage champions just cause.
You're going to seethe same champions played because that's the way it is.
Either get over it or don't watch
B00B001 votesMF Ashe Varus Jhin Thamkench Tarric Thresh Zyra Syndra Ziggs Camille Ivern Khazix Graves rek sai Rumble Maokai poppy gang plank Kennan Bard Le Blanc Rengar Jayce Azir Arianna Cork Karma Malz shen flora trundle cassiopeia ryze viktor ezreal nami tally twisted fate ekko olaf zac nocturne Swain morgana Katarina lee sin nautilus illaoi
thats just from NA and EU off the top of my head, and LCK have even more but can you count for me? i lost count....and I'm at work....think thats like 5 champs there?
DrCyanide1 votesOver a season it's OK. Enough changes happen patch to patch that way more than 20 champions get picked.
Where you have to worry is over a patch (or several patches that try to minimally change things), particularly the World's patch.
LEBLANKKK TIME1 votesFirst week WORLDWIDE lcs 85 champions were played it's still above 45 this past week which is over double the number you posted.