I agree! I was just about to post the same thing before seeing that you beat me to it. It does definitely seem like it could be defined as a modern remake of "Marty." There are definitely sufficient similarities. With that said, "Marty" appears pretty modern in its own right for being made in the 1950s! We discussed how modern it appears for its time when we watched it in my film class.

Modern day 'Marty'
^Yes, I always thought this too.
When theres no more room in Hollywood, remakes shall walk the Earth.

And, in some ways, it was.
Although while Danny's friends/brother were somewhat crass and obnoxious in their opinions of Teresa, they were nowhere near as flat-out asinine and repulsive as Marty's moronic sidekicks in the 1955 film.
That gave "Marty" a real mean-spirited subtext in that it left you with the feeling the best thing for him to do would be to tell his "friends" to F themselves and hit the Fing road - as long as he hung around with those losers his chances of ever meeting any kind of attractive or personable woman were exactly zero (actually less than zero any woman he was likely to get involved with while still associating with them would likely be a neurotic, self-loathing, immature, dependent ding-a-ling).
At least "Only the Lonely" ended on a hopeful note that Rose would allow Danny to step out on his own a bit and be his own man.

4. You ever seen Superman $#$# his pants? Case closed.

I recently read that it was written to be a pseudo-remake of Marty.

Agreed. I actually found out about Only the Lonely because I was looking for similar films like Marty.
I just rewatched the film tonight and it's still as great as the first time I watched it.