I see you've never travelled outside the US... it's better almost everywhere else.
The fact this happened means that it's better in the UK. As a frequent traveller out of LHR (London Heathrow international airport) I can see exactly how this happened and also understand it's not common.
First of all, you're conflating the responsibility of the various parties involved. Border Force is not tasked with ensuring the passenger is ticketed, their job is handling the security infrastructure and ensuring passengers don't have any dangerous goods or illegal items. The airlines are ultimately responsible for letting people on the plane, so they're the ones to blame here, not security or the airport.
Allow me to explain how it typically goes down when flying from Heathrow.
1. Arrive for my international flight 2 hours ahead of the scheduled take off time.
2. Check in to the automated check-in machines (if you have not already checked in online) and tag my bag.
3. Drop my bag off at the allotted desk.
4. Head to security.
4.1. Join the queue to enter the autmated gates, its never a long queue. Scan my boarding pass and the gates open.
4.2. Listen to the friendly Heathrow queue fuhrer who'll direct you to the shortest security line (seriously, they do a fantastic job of balancing the lines so no-one gets stuck in a 50 mile long queue, unlike say on the M25 just outside Heathrow).
4.3. Listen to the friendly Border Force crier who tells you what you need to take out, take off or keep in your bag (electronics and liquids can stay now, the LAG restrictions are also gone from most UK airports).
4.4. Join the queue for the rapey-scanner. It's never more than 2 or 3 people.
4.5. Enter the rapey-scanner when directed, put your arms above your head and legs akimbo like you're about to start strutting your funky stuff.
4.6. Collect your bag off the X-ray scanner after flighting your way past the belt lice who's bags went in after yours.
5. Get airside and realise that the entirety of the above took less than 30 mins and wonder what the fuck you're going to do with yourself for the next hour (but you know if you arrived with just 1 hour to go something would have gone wrong, it's sods law of airports).
6. After wasting time and paying a kings ransom for a drink in WH Smith's head to your gate and join a queue of complete fucktards who can't follow a simple instruction like "boarding group 3 only, if you're not in boarding group 3 please remain seated" who are also trying to carry on 6 tonnes of luggage.
7. BA have finally started turning away people who are not in the correct boarding group so when you eventually get to the front of the line, this is the first person who actually checks both your boarding pass and ID to ensure that you are the passenger you say you are.
8. Fight for the overhead bin space as every fucktard brings more luggage than they are permitted.
9. When the doors are finally shut, prepare for the 20-30 min wait on the Heathrow taxiway because some wombles have been blocking the construction of the third runway for 30 years because they're cockwombles
10. Sit back, relax and shut up. It's a long way to Canada.
Most countries have dispensed with most of the US instantiated security theatre. Hell, the worst part of airports outside the US (and even mostly inside the US) are dealing with other passengers. Automation has made the process of going through an airport even easier than it was in the 90s before the US lost it's shit and decided everyone else had to as well.
Now it's easy to understand how this occurred because the "man" in question was actually a boy of 12 of 13 depending on which article you believe and they know how he did it... He tailgated someone else through the automated gates and boarding process. Border Force had nothing to do with it and the Heathrow staff will just end up with another safety briefing as it wasn't reasonable or prudent for them to stop and interrogate a kid. As mentioned above, it's the gate agents who work for the airlines who will bear responsibility and even then, aviation works on a principle of "just culture" which encourages people to be honest about mistakes rather than blaming them making them so they won't have anything lumped on them apart from perhaps a new procedure.