Big problem for Everton is lack of mentality.
You look at their core players and it's not a bad 11 they can put out.
Coleman (o.k better before his broken leg but still one of better RBs in premier league and as good as some who sometimes play for top 4, Valencia/Trippier)
Mina (don't understand at all why he's now being benched as Zouma/Keane is dodgy as hell to me)
Digne (seems to be having a good season)
Gana (good stats and linked to PSG)
Andre GOmes (dipped a bit recently but rated by plenty)
Glyfi (for Everton level fine and when in form genuine matchwinner)
Richarlison (blows hot and cold but potential is huge imo which is shown by Brazil regularly calling him up now, not a central striker though).
Also got some promising young players like Lookman and Calvert Lewin but they need another 18 months as neither are established in first 11.
Everton's big problem is mentality. Look at how bad their record is v Liverpool. Look at how bad their record is at Old Trafford, Emirates, Stamford Bridge etc.
They played really well at Anfield, lost to a freak 94th minute goal and instead of chests out and winning their next 3-4, they've started feeling sorry for themselves and hence we get this inconsistant form.
They're like they were under Moyes. Or like we were under O'Neil. Or Spurs for a few seasons after Bale left. Some really good players that don't believe in themselves enough. Also not helped by how much stronger the top 6 is compared to even five years ago.
For all the stick Spurs still get about not winning trophies they at least believe now they belong in the top 4 every season. Guess Everton think Silva will be their Pochettino but I have my doubts on that.