There were actually multiple problems with the alert system that caused its removal, not just that the key was compromised or that users can get their information from other sources. The alert system was a major source of centralization; those who held the alert keys could send an alert to everyone in the network. This is undesirable for a decentralized system. The general agreement was that the alert system should not be networkwide, rather it should be software specific and up to the developers of their respective software to alert their users of ongoing events.
Furthermore, the alert system actually has a number of DoS vulnerabilities (i.e. node takedown bugs) that can't really be fixed without completely overhauling the system.
And the alert key being compromised is a significant concern. No one knows who actually holds the alert key and anyone who holds it could give it to anyone else if they so wished. Because of the DoS vulnerabilities in the Alert system, that is a major problem because if one person were malicious, they could take down the entire network by broadcasting one message to every node.
I also don't see why the alert system is a point of centralization, or why they talk about risk of keys being compromised. A new alert system could have been put in place of the old like this:
The alert text tells the user that something is going on. Check where you downloaded this application for more information from the developers of the same app, and where would that be? Github, bitcoin.org, mailing list. But you at least told the users to go check it out and they won't be in the blind.
I don't see any way to compromise this either!
For a while, there was significant concern that Gavin Andresen was going to publish an alert telling everyone to upgrade to Bitcoin XT. The alert text can have whatever the alert author wants in it, so he could have written a long statement telling users something that wasn't "go check where you downloaded this application for more info" but rather "Emergency, you must download software from this site NOW".
@laanwj is the only person merging PRs
No he isn't. Stop spreading that FUD. Jonasschnelli, MarcoFalke, and sipa have commit access as well and frequently merge PRs.