I've not been birding for as long. I've not got a record when I officially started, but it must be between 20-25 years.
One thing you mention is flocks of birds that have disappeared in your lifetime. Perhaps because I've never been aware of these massive flocks that it's hard for me to comprehend, after all if I've never seen them I can never know what it was like to have experienced them.
But I also live in a different place from you - the birds I experience on a daily basis are likely to be different from what you see. I live in a place where if I have a car both the west and east coasts of Scotland with their mixture of cliffs and rocky or sandy shores are accessible within a couple of hours drive, as are mountains and moor, river and loch, so I feel privileged to have such diverse land and seascapes so near to had.
I am aware that it is difficult to see some birds - I've seen a spotted flycatcher twice this year, but I really had to look for them. I've not seen a yellowhammer yet this year and it isn't normally easy to see them, likewise with the tree sparrow. I've not even heard, let alone see, a cuckoo this year.
But then you mentioned the willow warbler being scarce; by contrast you can hardly move near me for them, most stretches of woodland are teeming with them, with chiffchaffs in lower numbers among them.
However, I've been without a car now for almost two years now. Last year was the most depressing for me birding-wise because I hardly ever got to go to the places where I have seen the most diverse range of birds, simply because they were not very accessible without a car.
This year I made up for this by booking a holiday where someone could drive me around, and I booked onto day trips on boats for a similar experience. I've borrowed a car once and it was great to have the opportunity to visit some of those more distant places again.
I have also been birding at a much gentler pace than most people on this forum seem to be. Even after all the years that I have been birding, my UK list is standing at 176, and the most I've seen in one year is 120, although I'm currently at 117 for this year so may set a new record for myself. Some people on this forum report over 100 birds on New Year's Day!
However, it's not all about the numbers. I don't consider myself to be a twitcher - if a rarity does show up a few miles down the road then I'll probably try and see it, but I'm not likely to drop everything and visit Lewis because something rare has turned up there - in that regard I really like seeing birds in their natural environment rather than turning up windblown and ragged in a hedge 2,000 miles away from where it should be.
But while I've not seen that many birds in the grand scheme of things, and I say numbers aren't important, I still like to see new birds - who wouldn't? But I supplement my interest in birds with a wider interest in natural history - I enjoy going out on boats seeking cetaceans; I've started taking an interest in plants and flowers, and this is the first year I've really noticed orchids, helped in part by a woman who had a real interest in them that I had met while on holiday; butterflies and moths are really catching my eye now.
But I also started another thread about wanting to see all the penguin species in the world. This wasn't just about seeking out penguins, but was a way to widen my birding horizons - there's so much out there still to be discovered, although I only have limited funds, so I don't know how likely my goal will be. But at the end of the day, even when I was up in Shetland watching Arctic skuas and gannets, wheatears and merlins, there was still a simple pleasure in returning home and seeing rooks and jackdaws, chaffinches and goldfinches. Hopefully I'll never get to the stage where I get bored of such daily sights. Perhaps it requires visits to different places to really appreciate what you have at home, even if they are not as spectacular in terms of plumage or song or present in the same numbers.
But the UK does have its own spectacles, we have some of the largest seabird colonies in the world, we do still have impressive murmurations of starlings, you just need to go to the right places.
I must say that my own birding interest usually takes a dip during summer, only to be reawakened in autumn when the migrants start returning. But as I mentioned above, I've been taking an interest in other flora and fauna, so this maintains my interest in natural history right through summer as well.