Effects that looked amazing in the past often no longer look amazing. I remember thinking the dinosaurs in Jurassic Park looked real. Now they look like bad CGI with bad compositing. Part of that is the first time I see something, especially in the theater, if the story is good, I get sucked in and am not looking for flaws. Where as, years later when it's no longer exciting, because I already know the story or because someone said "go watch these effects", then those issues stick out. Knowing's effects were good when it came out and good enough if you were into the story and not trying to look for flaws. I agree though that watching them now they look subpar, especially the subway.

From the comments:

>Fun fact: this car scene was kinda an actual car chase. The director made the stunt man drive the car in the middle of street of Brooklyn without any acknowledge from the people and drivers there so they can capture real reactions. (It's illegal but apparently nothing happened to them)

(!) If that's true that's definitely why that scene is so good but hard to replicate. Though there are some props getting destroyed so maybe it's only true for part of the scene.

It was shot illegally (er, without permits). It really could not be done today:

“The car chase was filmed without obtaining the proper permits from the city. Members of the NYPD's tactical force helped control traffic. But most of the control was achieved by the assistant directors with the help of off-duty NYPD officers, many of whom had been involved in the actual case. The assistant directors, under the supervision of Terence A. Donnelly, cleared traffic for approximately five blocks in each direction. Permission was given to literally control the traffic signals on those streets where they ran the chase car. Even so, in many instances, they illegally continued the chase into sections with no traffic control, where they actually had to evade real traffic and pedestrians. Many of the (near) collisions in the movie were therefore real and not planned (with the exception of the near-miss of the lady with the baby carriage, which was carefully rehearsed). A flashing police light was placed on top of the car to warn bystanders. A camera was mounted on the car's bumper for the shots from the car's point-of-view. Hackman did some of the driving but the extremely dangerous stunts were performed by Bill Hickman, with Friedkin filming from the backseat. Friedkin operated the camera himself because the other camera operators were married with children and he was not.”

https://www.imdb.com/title/tt0067116/trivia

The director recently said he regrets the shot:

“As successful as the film was, I wouldn’t do that now. I had put people’s lives in danger.”

https://screenrant.com/french-connection-william-friedkin-ca...

> . Comparing the scene the subway crash to say, the train crash in Silver Streak (1976)[1] or Speed subway crash (1994)[2], I thought Knowing[3] was inferior and just looks terribly fake to me.

Speed probably looks best of the three. Knowing's train doesn't look real - maybe too fast, over blurred, missing reflections, whatever. Silver Streak looks terrible though, and is poorly directed.

Note that Ebert might be using "sensational" with either the first definition ("causing great surprise or excitement") or second definition ("presenting information with the intent to provoke intense excitement at the expense of other goals") given in most English dictionaries, rather than the third definition ("very good").