This is just my personal opinion: Mulder and Scully are bad friends, bad employees, bad neighbours -- I don't mean bad as in evil, I mean bad in that they are incompetent and terrible at their jobs and responsibilities. They are arguably worse than the sliders.
I'm not a fan of THE X-FILES. I do not like it. I respect its place in TV history. I am a student of THE X-FILES. I've watched it. I'm aware of it. I'm familiar with it. But I didn't buy that X-FILES casefile format episode guide because I like THE X-FILES or feel compelled to purchase the merchandise; it was an interesting project. I didn't buy THE X-FILES comics because I am a fan of the show; I liked the writer, Joe Harris, and felt he would do something strong with the series.
To review the sliders: Quinn was a terrible scientist and team leader in Seasons 3 - 4; Maggie was a terrible soldier in Season 3 and had a number of odd lapses in Seasons 4 and 5. The only reason Wade, Rembrandt and the Professor don't rank as terrible friends is because Wade vanished, Rembrandt only received four A-plots across Seasons 3 - 5 ("The Prince of Slides," "Asylum," "The Java Jive" and "Requiem"), and the Professor died before it went from bad to really bad.
But Mulder and Scully are arguably worse than the sliders. The sliders lost their original creators. In contrast, Mulder and Scully had Chris Carter writing them from 1993 - 2018.
Mulder is a bad friend and a bad partner: right up to 2018, he would not provide Scully, his colleague and teammate, with a desk in her office.
Scully isn't a bad friend to Mulder, but her attitude towards her life of public service is suspiciously inept.
Mulder and Scully are terrible investigators: they repeatedly fail to do anything more than observe paranormal events. They are also terrible public servants, repeatedly abandoning innocent people to die.
The most telling example for me when I was watching this show in middle school: in the Season 3 episode, DPO, Mulder and Scully encounter a psychotic teenager with electrical powers. By the end, Mulder and Scully have failed to find a way to charge the perpetrator with the murders or to depower or contain or imprison him; the next episode has them working on their next case, having presumably abandoned the entire state of Oklahoma to be ruled by a low-rent Electro.
By the Season 4 premiere, Mulder has a full picture of the alien invasion coming in 2012 and a weapon that is effective against aliens; despite this, Mulder makes no effort to share this knowledge or mount a defence and as late as 2008, Mulder is pointedly ignoring any need to fight off Colonization.
Mulder and Scully are terrible friends who are making zero effort to save your life or mine from an alien invasion and the fact that no invasion happened in 2012 seems less like effort and more like luck. If there are two people I don't want around in a crisis or a mystery, it's Mulder and Scully.
To be fair: I don't think it's entirely deliberate. I think that 90s TV called for running arcs to be siloed and Chris Carter wrote Mulder and Scully as passive observers because he found it unrealistic that normal humans could seriously battle supernatural forces -- but considering Mulder and Scully have been working since 1993, their total lack of professional development right up to 2018 is extremely poor.
Darin Morgan, Glen Morgan, James Wong, Vince Gilligan and even Frank Spotnitz recognized the problem that Mulder and Scully were overly detached and passive. All of them wrote scripts that made some effort to change this, but Carter would invariably revert to his factory defaults right up to the 2018 season's "Plus One" where Mulder and Scully are shockingly indifferent to a man fearing for his life.
Writer Joe Harris for the IDW comic book line made a determined effort to have Mulder and Scully actively focusing on the delayed but impending alien invasion only to be curtailed and cancelled.
As it stands onscreen: aside from short exceptions, Mulder and Scully are not good at being your friends and not good at their jobs. They are incompetent, ineffectual, indifferent, non-commital, uninvested, disinterested and have no regard for saving your life. That's not how the actors play their characters, but the show makes it clear: If you, RussianCabbie, were being tormented by a psycho with electrical powers, Mulder and Scully would show up, take notes, file a report, and then leave you to be further menaced and eventually murdered.
In the event that you are facing a psycho with electrical powers or an alien invasion, I suggest you skip calling Mulder and Scully. Call Sam and Dean from SUPERNATURAL or Peter and Olivia and Walter from FRINGE or Wynonna Earp or Liv Moore from iZOMBIE or the cast of DOCTOR WHO or Emma Swan from ONCE UPON A TIME, all of whom actually try to close the paranormal case of the week before going to the next one.
I would call the sliders, but I can't totally recommend that either given their poor job performances across Season 3 - 5.