I've never done anything but would really like to. This kind of event - relatively entry level, seems reasonable. Was also looking at the Lincoln 262 - longer but supposedly very flat.
The Tour of Cambridgeshire is definitely worth doing at least once. Loads of the folks on here have previously done it and some have deferred entries for this year as you'll have seen. I've done it three times; once as a 100 miler, twice as an 80 miler (back in the days when that was the longest option).
The whole closed roads thing has certainly spoiled me though - I'm now not interested in travelling far for any sportive that's not closed road; it really makes a lot of difference.
One thing I will say though is that one of the major selling points of the ToC of the course being super flat so you can go really fast; that isn't actually all that appealing to me now I've done it a few times. Those 30-40 miles in the middle of the Fens were the most boring part and if you hit a headwind at the wrong time, you're stuck with it with no place to hide for ages. If I do go back and do it again in 2023 or 24, I'll probably do one of the shorter routes that skips that middle section - but you should do the full course at least one time.