Its not this simple.
Even if we fast tracked the DRL, it would take, 9 years vs 13, and cost twice as much.
Fast tracking isn't some magical wand you wave and then suddenly things happen faster. It means paying lots of people extra money for prioritizing work. Anytime you want something faster you pay the price.
There are also huge engineering feats for this subway. It will be lower in the ground and go under more high development complexes (big skyscrapers) than any subway has been done in Canada. Tons of things, like the Enwave water system, hydro, gas, sewer, etc will have to be relocated and dealt with. Just because you dig deep it doesnt solve every problem avoiding this, you need ventilation shafts, emergency exits, stations etc.
Funneling all our money will mean the DRL will now cost $12 billion, rather than $6, for the portion from Queen to Pape, and will be here in 2027 instead of 2031.
Great, now we don't have any other transit solutions in the interim, and meanwhile the Yonge subway is getting worse, worse, worse.
We need the DRL, as well as solutions now, and in the meantime, like ATC, GO RER with full fare integration, express buses, on and off peak pricing, etc.
Putting all our eggs in one basket would be a huge mistake.
However, the Scarborough subway should be cancelled, yes, but that doesnt matter whether the DRL gets built or not. Its just a waste of money period.