It seems to me that the effective altruist movement over-focuses on “tried and true” options, both in giving opportunities and in career paths. Perhaps the biggest example of this is the prevalence of “earning to give”.

I would have guessed that the biggest example is the focus on poverty reduction / global health initiatives that GiveWell and GWWC have traditionally focused nearly all their attention on. E.g. even though Holden has since the beginning suspected that the highest-EV altruistic causes are outside global health, this point isn't mentioned on GiveWell's historical "top charities" pages (2012, 2011, 2010, 2009, 2008), which emphasize the important focus on "tried and true" charitable interventions.