Hyperbole.
If you had major problems going from 1.2.4 to 1.3.3, when you consider that 1.3.0 was released nearly 6 months ago (and it was its initial introduction that may have produced breaking changes, not so much subsequent releases), then if you had problems, you did so because you didn't plan and execute your upgrade correctly.
PhotoPost may well be an exception to the rule as strictly speaking it is not a XenForo add-on. And problems with PhotoPost integration have existed for a long time (Other gallery solutions are available...). The onus is on you to go a little bit out of you way to check with other PhotoPost customers and their developers as to whether there are any known issues.
As for everything else it is straight forward. By the sounds of it you aren't a fan of add-ons. That's fine. There's no point in you installing more add-ons than your community needs. Some people go way to far and regret it... (Don't they,
@DRE ) So I'm guessing you don't have too many. In which case it shouldn't be an arduous task to find out their 1.3 compatibility, or even just ask the developer. Did you read the XenForo 1.3 Upgrade Guide by
@Brogan? That covered the most common and disruptive issues you might hit during a 1.3 upgrade.
Without knowing exactly what your issues were, it's hard to be specific about how they could have been mitigated. But whatever the mitigation would have been, it wouldn't have been time consuming or difficult.
Please do not listen to
@jauburn's hyperbole. The crowd isn't wrong on this one.