I'm another who regrets planting stuff that hasn't survived!
We have a half acre rural garden that was just a mass of huge trees, weeds and overgrown laurels (I do regret the laurels being planted by whoever it was!) when we bought the house five years ago.
During the past five years we've been trying to create a garden, but the weather here is not suited to many of our choices. We've lost - loads of euphorbia, verbena (never re-seeds or comes back), ditto forget-me-nots, phormiums, dwarf conifers, alliums (100+ purple sensation bulbs lost), euonymus, verbascum, gunnera, kirengeshoma, calycanthus, cistus, trilliums, scabious, hellebores, camassia, clematis, ornamental grasses, actaea, erigeron, Japanese anemone, buddleia globosa, buxus, ilex crenata, lavender, rosemary, bay and lots of others I can't remember! Even my David Austin roses don't particularly thrive, with a few exceptions.
The only plants that are guaranteed to survive are bamboos, day lilies, tellima, persicaria and phlomis.
Our experience here has turned me right off gardening tbh...I mean, there's challenging and there's 'absolutely no point bothering!'