4 of the 13 spells can come from any school, I can think of 5 great choices from Abjuration off the top of my head and same for Evocation, plus the cantrips are not school restricted.
Here is a quick and dirty spell list
1st level: Absorb Elements, Sleep, Faerie Fire, Shield
2nd level: retrain Sleep for Shadowblade, Scorching Ray, Continueing Flame, Mirror Image
3rd Sending (evocation) and fireball, counter spell, Haste
4th Storm Sphere, Conjure Minor Elementals
At level 4 (or 1 for human) you take Ritual Caster wizard, more then doubling the potential amount of spells you can learn know, including spells like Find Familiar, Unseen Servant, Tensors Floating Disk, Illusionary Steed, Water Breathing, Rary's Telepathic Bond, Contact Other Plane. Between the subclass and the feat this is a very Gishy Character who can cast spells all the time, fights really well.
If that is not enough you can also take magic inniate wizard feat and perhaps racial magic feats as well.
So I don't see the issue.
I'm glad you enjoy it. I still disagree. Those evocation spells, with exception of fairy fire (and possibly fireball, as it is overclocked for its level), come on line too late for a 1/3 caster, given 5e's Bounded Accuracy and scaling Hit Points; thus bringing a knife to a gun fight. Damaging spells, the evocation school's main Schick, really depend on you having the higher level spell slots to make full use of them; they just don't have the same impact coming as late as they do compared to full casters. Sure they can be useful for the mooks, but usually there are better things you can do. And yes, they did do a cop out by letting you pick 4 spells from any school, but why have the restriction at all then? And yes, they do get good use out of their cantrips as well, especially with battle magic, no argument there. I'm not saying the class is broken or anything, it just feels a little tacked on, and evocation was not a particularly good choice for 1/3 casters (something like transmutation would have been better, as those spells provide a lot of utility that you don't level out of quite as much). I just prefer the more flavorful, though admittedly more specific, way of the paladin/ranger design.