> It really takes a solid 6ish months of earnest effort (AT LEAST 3x per week, probably more) to develop cardiovascular fitness. For some people, it'll take even longer

I don't think people need to suffer through 6 months just to start enjoy running. Yes when beginning running you suck (and also prone to injury); you basically have no zone 1-2 since your'e so out of shape, your zone 2 is basically a fast walk. So for newbies who train like that all runs become a zone 3 or even 4 - when you're totally new to running. No surprise they many time a) hate it b) get injured

I advise newbies to walk and run and try to keep HR very very controllable until you build up fitness. That should be both more fun and also more sustainable injury wise.