If you replaced Sabrina with Crystal in the offense it would only have have been a slight uptick and not enough to overcome the 3 consecutive FF defeats. In each of her 4 season in Oregon Sabrina led the team in FGA, sometimes by a fairly wide margin. Contrast that with UCONN who had 3 different players KLS, Napheesa, and Megan Walker leading the team in FGA while Sabrina was playing. In summary I agree with the last paragraph of
@domerduck post. Those UCONN teams were too talented and would have relegated Sabrina to at best 3rd offensive option until after KLS and Napheesa graduated. Having Sabrina and not Crystal also does not help with the UCONN flaws which proved to be fatal-lack of bulk & skill in the post position and the absence of a third guard to help the rotation after Saniya graduated.
UCONN would've been a much more dangerous team with Sabrina in the lineup the last 4 years over Dangerfield. Dangerfield was a good PG but she isn't close to being the distributor and playmaker than Ionescu is. A big problem down the stretch of 2017-2019 is that UCONN really didn't have anyone who could take the ball and go make something happen. They tried to make KLS into that player but she just wasn't a playmaker. Neither was Dangerfield.
If you look at it year by year for the FF loss, you have:
2017-Ionescu likely starts or at a minimum is the top player off the bench playing 25 mpg. She likely has a much bigger impact than Dangerfield did. In the F4 loss to MSU, Dangerfield had 1 point, 1 assist and 2 turnovers in 17 minutes. Ionescu very likely brings more to the table than Dangerfield did, and they were a poor decision by Chong away from winning. In the UCONN/UO game head to head, Sabrina scored 15 points, had 8 boards, 5-10 shooting and 6 TOs. Dangerfield had 2 points and 1 assist in 13 minutes.
2018-UCONN was loaded this year but was beat by a feisty and determined Notre Dame team. Dangerfield was solid as a PG but played quite poorly in the F4 game against ND until the last bit of regulation and overtime. She was 1-9 shooting until there were 21 seconds left and sat the last 5 minutes of regulation besides the final 21 seconds. She finished the game with 8 points on 3-11 shooting. Put Ionescu on that roster and the team likely has better ball movement and far better production from the PG spot, which was manned by Nurse (4-13 shooting) and Dangerfield (3-11 shooting).
2019-Sabrina was the best player in the country as a junior, so she likely is your top offensive option or at the very least is on par with KLS/Collier. UCONN had a big lead on Notre Dame in the 4th quarter (9 points) but ultimately ND stormed back and won. As you noted, UCONN didn't have an answer for ND's posts who put up 20/13 and 15/15/5 blocks. Even without size, Ionescu is a big upgrade from Dangerfield considering she is an excellent rebounder (UCONN was outrebounded by 17), and she likely puts up a better showing than Dangerfield, who finished with 4 points on 2-11 shooting, 0-6 from deep. Dangerfield did put up 9 assists and 1 TO, but they ultimately needed better production from the PG spot and that was the main weak spot in UCONN's offensive game. They still came close, losing by just 5 points in the Final Four. A few more rebounds and made buckets from Sabrina easily could've been the difference.
UCONN's flaws from 2017-2019 weren't Dangerfield, she was a good PG, but being able to upgrade from a good HM AA type of PG to a 2x POY at that position absolutely makes a massive difference and likely pushes UOCNN over the top considering they lost two buzzer beaters and another game by 5 points.
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Luckily I don't have this problem. Of course there were other possible outcomes, Mississippi State and ND could have won in regulation and it would still hurt as much. 
