Gardiner East to 401 East actually makes some sense, may not even have to to be tunnelled.
But for Allen Road to downtown? What are you on about... Most cities around the world get away with no controlled access highways downtown. That is an outdated auto lobby friendly, American-rooted urban planning embarrassment from the mid 20th century that should never be repeated again. Not to mention there is literally no room near Bloor for any highway tunnel exits, much less south of Bloor.
Cities like Seoul, San Francisco, Portland have actually removed some or all downtown highways.
I say all that as someone relatively supportive of elevated arterial ring roads as seen in Asia.
The highway removal trend is generally overplayed - the highways removed in most cases are relatively low use stub highways roughly equivalent to the eastern Gardiner which Toronto removed in the 2000's.
San Francisco removed it's elevated Embarcadero freeway in the 1980's when it literally collapsed from an earthquake, yes. But it was a duplicate route of I-80, a 10-lane highway running literally next door to it. They actually extended the US-101 freeway from the Golden Gate bridge closer to downtown a few short years ago!
Seoul has removed one highway, but still does not lack urban expressway networks at all. There is actually another freeway running east-west just 4km north of the Cheonggyecheon stream, where the highway was removed.
The ONLY example of a freeway removal in north america which is actually downgrading a major route, without a clear alternative, is the I-81 removal in Syracuse, and it hasn't even happened yet.
And even in Europe, London is the only major european city to really lack an inner city freeway connection, and even then it's basically moved it's modern downtown east to where freeway connections do exist (Canary Wharf).
Paris has the Boulevard Périphérique, a loop freeway about 9km diameter. This would be like Downtown Toronto having a loop highway extending north around High Park then east around Eglinton over to the DVP.
Amsterdam's downtown loop highway, A10, is about 5km diameter - like having a loop go from Bathurst up, then over along Dupont. (also, just saying, but this is Friday evening rush hour in Amsterdam.. lots of green!)
Madrid has one of the densest freeway networks of any city on the planet:
Barcelona has the B-10:
Frankfurt has a ~6km freeway loop around downtown:
Same with Prague:
And so on and so forth.
Berlin opened a new urban freeway extension, the B100, last year actually!
The difference between America and the rest of the world is that America builds 20-30 lanes of freeway capacity into it's downtowns, then a 1-2km loop around the CBD. Europe doesn't entirely lack urban freeways - it just builds fewer of them and builds them smaller, typically a single 6-lane loop highway surrounding the central city instead of just the immediate CBD. It ensures that it's never particularly far for cars to access a freeway while removing through traffic from the central city. They then build great transit networks and make limited, expensive parking in the downtown to encourage other modes while still ensuring those who need to drive can still do so reasonably efficiently.
Cities like London and Vancouver which completely lack inner city freeways instead need to have lots of very large arterial roads and have lots of commercial through traffic routed onto local roads. It doesn't work as well for pedestrians or cars.
Toronto's freeway network in the central city actually much more closely aligns with the typical European practice (The Gardiner / Lakeshore combo is a bit bigger than normal for europe, but not by much) than it is a typical American inner city freeway network.
Toronto has only 6 inbound freeway lanes of capacity - A typical American city of similar scale would have 20-30. IIRC Chicago has something like 30 inbound lanes of capacity into the core.
North American urbanists too often view the way to make progress in cities as punishing cars - banning them, tolling them, deleting all car infrastructure. Europe, and indeed basically all other countries, don't work this way. They still have car infrastructure, after all, many legitimitely need cars and trucks to run a modern economy, but instead, they build actual alternatives.
