From what everyone says on this forum, your experience is typical.
I made my first elderberry in 2021, so it's still a relatively new thing for me. My comments at bottling were 'sour, thin and tannic'; my wife thought it was like 'kool aid before you've added the sugar'. We almost didn't bottle it but decided we didn't have much to lose so went ahead. Tasting 15 months later (so ~27 months after vintage) was much more encouraging; 'assertive acidity but nice fruit (though a bit light); tannins mellowed out'.
That 2021 wine had 9lb elderberries and 2lb (Black Monukka) grape in 3 gallons, so ~3lb/gal elderberry. In 2022 I used 8.25kg/18.15lb elderberry in 6 gallons, so similar amount of fruit but I did an initial 4 day cold soak and drained/pressed after a week when brix was still relatively high. Tasting notes at bottling were 'Fruity, rounded with unobtrusive tannins', I figure I have at least another 9 months to go before trying my first bottle.
My 2023 version had a lot more fruit: 16.15kg/35.5lb in a 7 gallon batch, so a little over 5lb per gallon. I did the same 4-day cold soak and drained/pressed after a week. Too early to tell how it will turn out, but taste at 5 months after ferment was 'Intense elderberry flavor and not too tannic'.
What recipe did you use? Curious to compare and contrast...