I don’t have the expertise to debate it, but I think it’s a bit odd almost no one has mentioned any lines from the last 20 years. Idk if it’s scoring being down or players not getting being HOF yet but still.
Looking at results from naturalstattrick (which restricts looking at forward lines to 3 seasons, and obviously only has this data from 07-08 on), the Bergeron-Marchand-Pastrnak line over the past 3 years at 5v5 is 1500 minutes, a 60% Corsi for, 81/57 GF/GA (58%), 55% high danger chances percentage on basically a 100 PDO. Looks like 60% offensive zone faceoffs too.
The Caps line of Ovechkin-Backstrom-Semin during their 3 year peak of 07-08 through 09-10 is a bit skewed because when they didn't start a game together, they were a line when Washington was trailing. Still, they had 650 minutes together at 5v5, rocking a 60% Corsi for, 55/19 GF/GA (74%), 58% high danger chances for on a PDO of 106. The on-ice shooting percentage for them was 12.8% - kinda ridiculous. Their offensive zone faceoff percentage was 66%.
Ovechkin and Backstrom without Semin during that period had 2040 minutes together, a CF% of 58, a 113/78 GF/GA (59%), 54% HDCF percentage on a 101 PDO with 58% offensive zone faceoff percentage. So they had slightly worse attempts and chances, but Semin really juiced their actual goals for - their GF/60 rate is a massive 5.07 compared to 3.32 with just Ovechkin and Backstrom.
Of other recent lines, you have the Getzlaf-Perry-Ryan trio in Anaheim, and over their peak seasons from 08-09 through 10-11, they had 1544 minutes of 5v5, 51% Corsi for, 90/52 GF/GA (63%), 53% HDCF percentage on a 104 PDO. Offensive zone faceoff percentage down quite a bit from the other two lines, at 53%.
The Sedins+Burrows line in Vancouver from 09-10 through 11-12 had 2080 minutes together, a 58% CF, 132/59 GF/GA (69%), 60% HDCF on a 105 PDO, with a massive 75% offensive zone faceoff percentage. Vigneault just never started them in the D-zone - their offensive zone and neutral zone faceoffs per 60 are in line with the Bergeron line, they're just missing 10 D-zone faceoffs per 60 that the whole Bergeron line is taking.
Beyond that, I think it has more to do with coaches tending to keep a duo together and mix up the 3rd person. Looking at Tampa, Kucherov+Stamkos have over 1800 minutes together over the last 3 years, but only 42 minutes with Point as well. Crosby has great numbers with Guentzel, but different third wheels, and same with McDavid, Draisaitl and Nugent-Hopkins.
For what it is worth, from 07-08 through 09-10, Crosby and Malkin had 880 minutes together as a duo 5v5, with a 51% CF, 68/41 GF/GA (62%), 58% HDCF percentage on a 104 PDO, with 58% offensive zone faceoffs. Looking at their other 3 year samples more recently results is less than 300 minute sample sizes. That GF/60 rate is 4.64, which is in the same ballpark as the Caps line, with a similar boost over Crosby's 3.18 GF without Malkin and Malkin's 2.84 GF without Crosby.
I'm naturally pre-disposed to think the Caps line is the best post-lockout line, but looking at the underlying numbers seems to justify that moniker.
Edit: a quick gander at Kopitar-Brown-Williams from 11-12 through 13-14 has a 62% CF, 52/32 GF/GA (62%), 62% HDCF and a 100 PDO, with 55% offensive zone faceoffs.