It takes a stretch to suggest that it was the plane described in the article rather than the Jet Age that marked the transition to what could be described as a "modern airliner".
Similarly, the lack of first generation jets flying today has a lot more to do with metal fatigue and the maintenance requirements that resulted than the notion that small slow planes with less to go wrong with them are a more modern design. Suspect there are more retro rotary phones in service than first generation iPhones today for similar reason, but I'm not sure that weakens the iPhone's claim to be the first modern mobile phone.
But were these modern airliners and which was the first in that class. <shrug>
Think there's a decent case for the Vickers Viscount in the early 1950s too, as the first airliner with a modern turboprop engine type, with speed and range and passenger experience (big pressurised cabin) comparable to small airliners still being built, unlike the 247 or DC-3.
Don't forget engine efficiency. Early jets engines were extremely fuel hungry, and even today in the span of a decade engine efficiency has drastically improved.
Difference is you can keep an ancient DC-3 around for occasional use with relatively basic maintenance, whereas a second generation jet or turboprop comes with service and life-limited parts requirements to make it considered airworthy that would cost more than the aircraft is worth...
The point being that the term modern is most certainly subjective and definitely has usage that is different from "contemporary" even though the latter is how people often read it.
If you want to start earlier, I'd personally pick the Super Constellation so.
The Comet airframe was inherently limited by the decision to embed the engines -- de Havilland Ghost turbojets -- in the wing roots. Obviously this wwas great for drag reduction, but it made it difficult to modify the design to accommodate other, more efficient/economical engines. In the end, the attempt to refit the last Comet-descended airframes, the RAF's Nimrod MRA2's to MRA4 spec with Rolls-Royce BR700 turbofans in the 1990s/2000s failed due to spiraling prices because the higher diameter turbofans required substantial redesign/reworking of the wing roots. More here:
https://en.wikipedia.org/wiki/BAE_Systems_Nimrod_MRA4#Delays...
Now compare this to the succssful engine retrofit program for the USAF's KC-135 fleet, which kept them in service for a couple more decades:
https://en.wikipedia.org/wiki/Boeing_KC-135_Stratotanker#Eng...
Having the engines hung on pods below the wing (or alongside the fuselage) makes them inherently easier to service and easier to upgrade (although problems can emerge if you push it too far, as witness the Boeing 737 MAX crashes).
This isn't to dismiss the Comet completely: it was a pioneering design, broke ground, and was the first trans-Atlantic jet airliner in service. But it had design flaws beyond the infamous metal fatigue problem.
I don't see engine retrofits as being disqualifying though, as modern engines seldom retrofit to older wings even if the original engines were podded (the MAX wings were a new design), and the turbojets the Comet was supplied with were much closer to modern engines than the 247's pistons anyway.
The monocoque aluminium shell and cantilevered (across the aisle!) wing of the 247 was its novelty, but I'm not sure cramped piston engined 10 seaters with 200mph maximum speed are really what people think of as "modern airliners"...