You should be more disgusted at the laziness of modern intelligence gathering, if the only way to find out what is going on it the work nowadays is to capture everything and hope you find something useful, then the spies have a lot to answer for!
Reading other people's mail is a long and dishonourable tradition in government circles. And is often an excellent way of finding out what's going on. By-and-large it's also a great way to find things out that doesn't risk getting people killed. Whereas spying, in the 'James Bond' sense of wandering around where you're not supposed to be, is rather risky. In the case of the more common type, which is mostly legally resident 'diplomatic' staff recruiting locals for information - the risk varies by the regime you're spying on. But there are plenty or governments who execute traitors.
So to give some examples. Kim Philby betrayed pretty much all of Britain's Cold War intelligence networks in Eastern Europe. I remember reading that between 50 and 200 of those people were shot. I've seen rumours from multiple sources that the GRU burned Oleg Penkovsky alive, after he'd handed over intel on Soviet nuclear readiness during the Cuban Missile crisis. That could just be a myth to frighten others of course.
Despite all the attempts at spying though, I can't remember much in the way of political intelligence from either the Cold War or WWII. Admittedly the US may have been doing rather well at spying on microwave relays, so we may have done better in the late Cold War. But if you read a book like 'The Secret State' (by Peter Hennessey), it's both fascinating and terrifying how little the Western governments knew about Soviet politics and intentions.
You can find out lots from looking at stuff. What the military are up to, and what kit they have. What facilities have been built. But that only tells you what a state can do or is doing. Not what it will do, or intends. Hence we 'knew' Saddam had WMD, because we'd found loads of it in the 90s, and only destroyed some of it. But we had no political intel, to tell us he'd apparently decided it wasn't worth it and had got rid of it. Which was a costly mistake.
We also know that Iran has a nuclear program. But I've no idea what intel we have on why they've got it, and whether they intend to bargain it away, build it for safety, or even use it.
The great thing about reading internal government documents, is that you get to find out what the government are really thinking. And saying to each other. It's quite rare to find people at that level willing to spy. And even harder to get access to them. We spent the latter part of WWII reading lots of the German HQ-level traffic, and this gave a much more useful idea of what they were up to, than you can guess from looking at where troops are actually based.
Not that I'm defending reading ordinary peoples' mail. But spying on foriegn governments is what we have intelligence services for. And I'm perfectly happy for that to include allies like Angela Merkel. The German government's position on various global and European issues is vital to British national interests. And no nation with a foreign intelligence service itself has any right to complain too much when it gets spied on. Well the game is, you complain loudly for a bit, for appearances, and maybe get some concessions, then go back to business as usual.