It is quite annoying. Especially if you try to thief from Gnomes, you spend most of the time just running after the NPC itself. :'D
But in a way, it's the "balance" for thieving. Otherwise it would be so easy.

There were few places at grand tree where u could have trapped 3 gnomes in 1 spot , u wouldn't run out of gnomes almost never , u didn't have to move at all , if u fail u 1 hit the gnome. And it pretty much was balanced . It was one of the best skills to semi afk since u didn't have to bank at all , when ever i didn't feel like playing the game i went there and semi afked , now when ever i dont feel like playing i just log out or don't log in  .  There are 15+ players who are 200m exp in thieving or rly close to it , some of them hide their stats . All of them got 200m exp on the 3 spots at grand tree , but the newer players have to achive that on a much harder way and they need to rly be focused on the screen now . So imo something has to be done about theiving  .
If u wonder why they did remove the 3 spots at grand tree (removed 2 out of 3 gnomes in each spot), it's not cus it was op since the 3 spots where there from the beging , it's cus they caught a guy botting on 3 accounts there (max accounts btw) he lended hes 3 accounts to a friend who botted on all 3 accounts without hes knowledge. And i think it's unfair to punish us legit players cus of  botters .

Yeah I was a tad bit frustrating leveling on the Gnomes. So I ended up going back to watch men and they seem a bit faster experience since you don't have to walk around. But it is what it is for now so I guess I'll stick here.

If u are 82+ theiving go Ardougne castle and go upstairs ( u need 1st to kill the 2 paladins downstairs) theres a small room with 3 paladins in , its better xp and gp then watchtower at 82+ lvl . At 92+ thiev heros

The grandtree spots were nerfed a little. I think there are now only 2 gnomes to thief instead of 3.
But thieving is very easy and quite fast to level no matter what. Even when they run away like that.

But that's because most likely a lot of people were half afk botting them so they did not get caught but still got easy xp. At least that's what I imagine people have done.