You can't get thousands of variables with all to all connectivity on a quantum annealer. The noise will kill it. I.e. you will never have such a device with reasonable coupler precision.
The techniques for decomposing a problem and solving the sub problems are a big (exponential) overhead because of frustration effects which require you to look at the entire problem at once.
And for context the PUBO -> QUBO mapping (high order to low order) + topology embedding can blow up the number of variables by an order of magnitude or more. The solution space scales exponentially with the number of variables so a naive solver will again deal with a messy overhead.
Have you seen their hybrid system they just released? https://www.zdnet.com/article/this-cloud-service-lets-you-us...
Looks like it's a strong contender for people who have bigger, higher-connectivity problems that want to get ready for when the quantum processors are bigger.