I'll make two different points:

you get to call yourself CTO for a time, alongside the CEO/Founder and COO, working out of your friend’s garage, but the startup goes belly up. You apply for jobs at mid-sized companies but nobody takes your “CTO” experience seriously, and rightfully so.

Yes, if you are president/director/CEO at your own company or at an organization that was founded by you and your friends, I'm not going to take your title very seriously. Most likely, the title doesn't mean anything because you gave yourself that title. Or it doesn't mean much because you didn't have to go through the standard path of earning it.

Alternatively, if you have a moderately impressive title at an organization I've never heard of before, then it depends on what the organization does, how large it is, and what your role was. Being the manager of a 4 person team at a 25 person company (and the company has survived/lasted for several years by being as least somewhat profitable, rather than constantly burning investor money) is fine. It isn't as impressive as being a manager as Pepsi or 3M or Volkswagen, but it is fine. Depending on how much effort I spend to understand the your role at your previous organization, I'll discount (or increase) my estimate accordingly.

All else held equal, I'd be much more interested in interviewing someone who was project manager at a company I've never heard of than someone who was CEO/founder/director/president at a company I've never heard of that they helped to found. (EDIT: what I mean is that I'd prefer an modest title that is earned than a very impressive title that is easily obtained.)

Epistemic status: pepperoni airplane, includes reasoning about my blase and bohemian risk tolerance and career path which probably doesn't apply to e.g. people with responsibilities. I think it'd be really hard to proceed with this question in a non-anecdotal way, e.g. employers being cagey about the reasons they decline hiring someone due to legal risk as a barrier to creating a dataset. 

I took a 6 month sabbatical at EA Hotel to do some AI safety things smack in the middle of what was supposed to be a burgeoning IT career. I received zero career advice telling me to leave that startup after a mere 8 months, but I'm good at independent study and I was finding that in my case the whole "real world jobs teach you more than textbooks" thing was a lie. So off to Blackpool I went, here's the one consideration: I didn't feel like my AI Safety Camp Five project had freedom to be too mathy, I felt like I needed to make sure it had a github presence with nice-looking pull requests because while I was earnestly attempting an interesting research problem, I was also partially optimizing for legible portfolio artifacts for when I'd end up back on the job hunt. 

When I got home, I had a couple months left of the SERI internship, and toward the end of that I landed an interview at a consultancy for web3 projects (right groupchat right time), and crushed it using some of my EA Hotel activities (the leader of the consultancy ended up mentioning reinforcement learning on sales calls because of my AI Safety Camp Five project, though no customers took him up on it). I kinda borked my SERI project, so took a confidence hit as far as alignment or any kind of direct work was concerned, so retreating into E2G was the move: it was also great brain food and exposed me to generically kickass people. The point is that EA was not a negative signal, even a totally weird-sounding sabbatical at a hotel in a beach town scored no negative points in the eyes of this particular employer. The takeaway about my AI Safety Camp Five project is you can optimize for things legible to normies while doing direct work. 

If you have way less bohemian risk tolerance than me, then your EA activities will be way more legible and respectable than mine were at that time. 

It's kind of like what they tell people trying to break into IT from "nontraditional paths"-- the interview is all about spin, narrative, confidence. IT managers, in my experience (excuse another pepperoni airplane), can get a ton of useful information from stories about problem solving and conflict resolution that take place in restaurants or film sets! Unless I'm deliberately making the least charitable caricature of HR, I assume that if you talked about some project you tried for a while with this social movement of philosophers trying to fix massive problems in an interview you'd get a great response. 

I have no expertise in this but surely an organization's credibility to non EA employers will depend on a lot more than its beliefs, e.g. how old the organization is, how many employees it has, any signal of external endorsement (e.g. lots of money moved if it's grant making org, receiving a large grant if it does substantive work, having some academic affiliation, etc).