They always say, don't they, that you build a successful team from the back.
Whether that's a cliché or not, it's safe to say that we're pretty solid at the back. We've got that base to build on.
Let's hope that we see the progress we need to going forward now.
Pickford is currently enjoying the best form of his Everton career. Important to note that up until something like the end of February, most people wanted him gone... maybe he's turned a corner. Maybe. Behind Pickford we have no depth (Olsen's loan is up in the summer and I doubt he'll want to come back).
Coleman is pretty much done. He's been a great servant to the club, and was arguably the best RB in the Prem at one point but that point was more than a couple of years ago now and it isn't coming back. Behind Coleman we have Holgate, who is a mediocre RB at best.
Mina has some real strengths, but is injury prone and on very high wages. In fact, his wages are such that I would say he isn't delivering good enough performances consistently.
Keane is an incredibly limited player in that he is excellent at a very narrow range of skills. He can't play a high line, he has no pace, he is agricultural with the ball, he is the epitome of a confidence player. He is great at sitting deep and endlessly heading away crosses, but if we continue to play with a back line sitting deep then we will continue to underwhelm.
Godfrey... Really, really promising. He's got a bright future ahead of him and if he continues to develop at the rate he has done this season, he's a year away from being our best CB.
Digne blows hot and cold. When he's switched on he is excellent bordering on elite, but he isn't always switched on. I do suspect that if we recruited a decent RB we'd actually see improved consistency from Digne as opponents wouldn't be able to flood our left side to stifle Digne, because they won't be able to just ignore our right side (as many opponents have done this season). Behind Digne as depth we have the pretty much untried and untested Nkounkou - who knows, might be great. Might be Pistone.
TL,DR: I fundamentally disagree with your assertion that we are solid at the back. We are at least a starting RB away from being solid at the back, and that assumes:
a) Pickford improves
b) Mina stops getting injured all the time
c) Godfrey's continued development carries on completely unhindered.