This has never been one of my favorite Fleetwood Mac songs, but I do listen to it occasionally. And every time I'm struck by how perfectly the bass sits in the mix. It has a lovely thick, round sound which cuts right through, and every note is perfectly even with the perfect attack. 
 
I'm guessing a huge part of it is that it's a great quality performance. But what else? Is that evenness mostly performance or have they dialed in the perfect compression settings? And can I hear some saturation in the mids? Would you isolate the mids from the lows to saturate them in getting a sound like this? 
 

 
 

One trick I saw on a mixing course was to put a limiter/gate on the bass track triggered by the kick drum, lowering the bass volume when the kick drum was playing, but allowing the bass to be at a slightly higher volume when the kick wasn't playing.
 
This effectively allowed the bass to be at a higher volume without sounding boomy and hogging the mix.
 
What was surprising, was that the perceived volume of the bass when the kick drum was playing didn't sound any different to the higher volume when it wasn't... but the bass sat in the mix MUCH better.

that fm lp was mixed/produced by lindsey buckingham, so maybe try and find any mix tips etc from him? there's an sos article here but not for that track https://www.soundonsound.com/techniques/inside-track-buckingham-mcvie-feel-about-you

msmcleod
One trick I saw on a mixing course was to put a limiter/gate on the bass track triggered by the kick drum, lowering the bass volume when the kick drum was playing, but allowing the bass to be at a slightly higher volume when the kick wasn't playing.
 
This effectively allowed the bass to be at a higher volume without sounding boomy and hogging the mix.
 
What was surprising, was that the perceived volume of the bass when the kick drum was playing didn't sound any different to the higher volume when it wasn't... but the bass sat in the mix MUCH better.

Well I guess that would be sidechain compression - it's very common (some say mandatory) in EDM to sidechain the kick to the bass compressor, and it does what it says on the tin. However I'm not sure I like the effect, and I try to write bass lines around the kick so that they're not (or rarely) playing together. 

pwalpwal
that fm lp was mixed/produced by lindsey buckingham, so maybe try and find any mix tips etc from him? there's an sos article here but not for that track https://www.soundonsound.com/techniques/inside-track-buckingham-mcvie-feel-about-you

I didn't know it was produced by Buckingham, thanks!

sounds about the same live,
which tells me,
it's the player and the player's bass and rig.

John McVie always seems to play just the right part, nothing more.
Which is awesome.
In listening to this song, I'm struck with the limited amount of sustain
that he allows most notes to carry.  It really works for this tune.
The quarter and eighth  notes  are delivered with just the right amount of punch and then they're gone, leaving
 sonic space for whatever comes next.  In my opinion, the magic is all in 
his hands. Great muting technique.  Good gear doesn't hurt either :)

Yeah it's a remarkable performance, really solid, almost as if it's been quantized (which of course it hasn't). 

tagruvto
John McVie always seems to play just the right part, nothing more.
Which is awesome.
In listening to this song, I'm struck with the limited amount of sustain
that he allows most notes to carry.  It really works for this tune.
The quarter and eighth  notes  are delivered with just the right amount of punch and then they're gone, leaving
 sonic space for whatever comes next.  In my opinion, the magic is all in 
his hands. Great muting technique.  Good gear doesn't hurt either :)

Excellent point. He really controls where he keeps it tight to the kick and where he opens it up a bit. Then again, what would you expect from a band named after its rhythm section?

Hearing it as a combination of a great player with a great arrangement for "sitting in the mix". No guitars muddying things up, mostly breathy female vocals/stacks, a spare drum part and twinkly bits panned pretty hard. I recall McVie using an Alembic going direct quite a bit in the modern version of Fleetwood Mac which could have something to do with it but given LB's documented tendency to go off the deep end at times, would not be surprised if multiple tracks with parallel processing were used.