Well, generally, when people who use a team of OU/UU pokes come up against a team full of ubers, they're at a massive disadvantage. Is there really any fun in effortlessly crushing far weaker pokemon with your ubers? I don't think winning is something to boast about when you use Ubers out of their tier. However, that feeling when I beat someone using all ubers is just awesome.
actually it seems the majority of teams i go up against have ubers too, even in this new playthrough. I see a ton of Zekroms, Reshirams, Rayquazas, Fairy Arceus, Darkrais and Kyogres, or teams of the Gen 6 Legendaries including Gen 1.
However a common issue I see, also how I can tell they are New/noobs is sometimes is some do noobish builds.. i.e. a team of 100% dragons (zekrom, kyurem, palkia, rayquaza, reshiram, dialga) which leaves them EXTREMELY vulnerable to ice/fairy types.. basically when i see a team like this (which is often as of this new replay), i just set my choice spec'd Xerneas in the center and do a Dazzling Gleam to insta-kill all three of their Dragons. then I have Mewtwo to Aura Sphere Dialga and Reshiram (the only 2 dragons Xerneas isn't super effective against).
So that's pretty much what I mean by they don't stand a chance... they are probably not experienced or have tactics or good prediction skills yet, regardless if they have a perfect Uber team built (or even a mirror/similar team to mine).
but the #1 way I know they are "new" is because it says so during battle, it shows how many battles your opponent has done, and I've noticed that majority say under 100, where as before when i had 1000+ battles on my record, i was going against mainly people who had hundreds of battles as well, so this is why I believe the battle spot system sets up special slots or tiers based on # of battles you've done.. maybe when you hit over 100 or some number, you start only fighting others who hit over X number of battles too?
Also if i do go against a team of UU/OU, etc.. i tend to "go easy" on them sometimes.. i'll try to send out my talonflame, mienshao first and let them take care of business. or sometimes i'll send out my 3 legendaries but purposely use the neutral effective moves against them..
However I do have to say, of my over 1700 battles on battle spot, it's very rare to come across a team without at least 1 or 2 ubers, even if it's just an event Blaziken and a Gen 6 Legend or a Blissey and Shuckle with a trick rooming Slowking/Reuniclus.. Teams without ubers just don't really have a place in "Free Battle" on Battle Spot, since it's flooded with Legendary & Uber teams.
Rating battles, thats a different story since legendaries are banned, so you'll tend to see more NU/UU/OU/mixed teams on there.
Lastly, even without an "Uber team" it is possible for a good strategist to dominate in free battle. I have personally faced a handful of non-uber teams in battle who were able to destroy my team either using tactics such as double fake out, while their 3rd pokemon trickrooms or takes out one of my primary Pokemon (Xerneas or Mewtwo), or use things such as quick guard to make talonflame useless due to it's galewings ability priority getting blocked and also blocks Arceus' main attack, extremespeed or they will wideguard to block Xerneas' choice spec'd dazzling gleam (making Xerneas useless since it's stuck using only that attack) or other various tactics and "right on the money" predictions.