Is this a flaw you would accept?
Out of hand, it seems a bit weak for a minor flaw.
It is somewhat similar to the Bjornaer's inability to bind a familiar (although familiars can be much more useful than a talisman). More to the point, the flaw Weak Enchanter halves all lab totals involving enchanted items (including Talisman but also charged items, lesser enchanters and invested devices). Of course, Weak Enchanter is particularly strong as a minor flaw.
So I might consider it; I would be more likely to accept it if it was a good fit for a particular concept.
Note that the same reasons you mention might also mean that the virtue include the inability to bind a familiar, so these two could be packaged together to make it more likely that the flaw is acceptable (with a name like Bound Gift or something like that).
A package of no talisman and no familiar I'd find almost too punishing for a major flaw, personally, let alone a minor.
I have to agree with Arthur -- I think it's worth somewhat less than a "normal" minor Flaw. Not being able to bind a familiar is definitely much more serious. On the other hand, "No invested devices (including no Talisman)" seems about right for a minor Flaw.
It's a bit too good to be a minor flaw.
I suspect that No Familiar was considered equivalent to a minor flaw, and this is more severe than No Talisman. Cord bonuses are really good, and familiars are flavorful fun. Oh, yes, and RAW, no Warping from near-persistent effects enchanted into the Bond. This is a severe minor flaw to take, but I think it is closer to a nasty minor flaw than a reasonable major one.
A talisman can be a huge time sink and also a huge Vis sink, so a character who takes this flaw gets a lot of time to pursue other stuff and can spend his Vis on other stuff, too. The attunement bonuses aren't so overpowering that not having a talisman cripples a character. Mechanically, I don't think it is quite as strong as some minor flaws, but they can't all be equal.
This is probably a great flaw to add from a Twilight episode that went sideways that involved the talisman in some way, such as including the attunement bonus. The flaw would remove the benefit of all attunement bonuses, but the effects would still be accessible. I'd also prevent adding effects if there is unopened space that exceeds the shape and material base cost.
What if, rather than focusing on the "No Talisman" aspect, you make the flaw more about an inability to take advantage of S/M bonuses? No attunements, no Lab bonuses for S/M, no casting total bonuses for Potent spells you learn, even if you have the casting items, etc.
No Talisman alone seems too weak for even a Minir Flaw
However Jason's suggestion of never being able to use S&M bonuses seems harsh.
I have a feeling Tellus considered this suggested flaw for a lab-rat type character. Someone who spends most of his time in a lab and designs devices rather than go outside and use spells, like a Verditius perhaps?
However if a Verditius has sufficient Philisophiae he can use the "Verditius Runes" in lieu of S&M bonus and simply not care about that. Does than mean the Flaw is still a bit cheap because the Verditius can more or less ignore not being able to use S&M of items? Yes and no, because if his Philosophia is much lower than his Magic Theory (which is likely) then he does not maximize his potential bonus.
But having this Flaw mean the Verditius can't use Runes either then a good part of his House Mystery is irrelevant, and that seems unduly harsh.
Christian apparently knows me too well.
I would not accept this flaw myself. I would consider it an arguably 'free' flaw point for eg. a verditius. Or really largely any other magus not focused around combat-via-penetration.
But talismans appear to be rather more popular than I'd expect.
I'm glad to see that I'm not alone in thinking that'd have been a bit cheap.