Ahhh.. creating new breeds.
Yes, all the breeds we have were originally mixed breeds.
However on the whole they were created in a fairly short time frame by one, perhaps two people initially, who could breed intensively and cull hard (and yes, I do mean by killing those that didn't make the grade).
THey could do this because they were rich aristocrats, landed gentry, those with time, space and money to burn and bugger all else to do.
Breeding in this way meant that they achieved their goal usually within their lifetime, had one or two people to carry on that very specific goal who would not veer from it, and no one who would not adhere to that goal got their hands on a pup.
This doesn't happen now, it can't - people tend not to have the space or time or money to do it. They don't want to do it by themselves, they can't do it by themselves so they involve other people.
Other people have lots of different ideas, and no one these days can stomach killing dogs because they don't make the grade. So they rehome and hope that people will neuter... and not breed from them and most do but some decide to go their own way with a breed using someone elses 'rejects'...
And so it takes a long time to get a new breed to breed 'true' (ie the offspring will definitely look like the parents and fit that breed standard to a very high degree).
Breeds like the wolf-a-likes - the Northern Inuit/Tamaskan/Utonagan - these started out as one attempt to make a dog that looked like a wolf... and people had differing ideas and fell out and bred from dogs it had been agreed not to breed from...
Like the Old English Bulldogge/Old Tyme Bulldogge... same thing.
And then theres those who just breed any old dogs together and slap a name on and call it a breed (XL Bullies) because their agenda is somewhat different.
Cockerpoos and Labradoodles are not going to become a registered, true-breeding 'breed' any time soon because very very few people are attempting to do that and those that are are not working together in a way that will survive outwith their own lifetimes. The money to be made is in producing early gen x's, cockerpoo x cocker, poo x cockerpoo etc, so that is what most people are doing.
If you're still outcrossing, you're not attempting to produce a true breeding pedigree.
Some folk HAVE produced a recognisable breed in their own lifetime, Brian Plummers 'Plummer Terriers' were for a time true breeding and highly recognisable. But since his death things have wavered off course, few people want them, fewer want to stick to his vision... or do the things he did to achieve his goal!