Cyser help, please

So long before I joined the forum I made a 1 gallon batch of spiced cyser (my first). I used half a gallon of orchard cider, a pint of raw honey, and used a couple cloves, some raisins, and a bit of tangerine zest in the cider while it was hot, before adding the honey, but never boiled. Topped it off to a gallon with water. This was about 18 months ago now...

It looks great, but still has a crazy tartness to it that, as a mainly beer brewer, tastes "young" to me. Also, there's an odd... I don't know... plastic? flavor to it that I can't quite put my finger on.

In a total mead noob, but any ideas what I'm missing here?
Vitals: used premier cuvée yeast. FG was 0.940, ABV just over 18%. Tasted at 12 mos and at 18 mos. same flavor present, though better at 18 months.

What am I forgetting to tell you that would be helpful?

Any thoughts on this? Would really appreciate feedback. Could a year and a half leave it as still young? Could it be the spice additions? All of those were really small (3 cloves, 1/2 tsp cinnamon, 10 raisins, tangerine was a clementine, and not even all the zest from it).

Some Apples have quite a bit of Malic acid in them and if your Cider was apart of that class of apples that would account for the over tartness. Ether Malolactic fermentation should be performed by introducing the correct bacteria to the Cyser to get rid of some of the Malic acid or use Lalvin 71b-1122 yeast for the original fermentation which metabolizes Malic acid to remove that tart flavor.

The rest of the ingrediants seem fine. Whole cloves are more comonly 1 - 2 per gallon but 3 should not be terrible.

18 months is plenty of time IMO. It should be quite enjoyable. All my stuff seems really good at around the 7+ month mark and is really good past 12 months.

So I think you are a little high on the acid. If you add in some Sorbate and K-meta/Camden to stabilize then add honey to add a little sweetness it will balance out better.