The biggest disadvantage in my mind of target date funds is that you can't optimize for tax efficiency. For instance, claiming the foreign tax credit, keeping bonds in tax-deferred or tax-free accounts, etc. Tax loss harvesting is also much less precise. But I think of these as pretty advanced investing concepts that may be more than you want to deal with, and the advantages of target date funds doing most of the work for you can easily outweigh these disadvantages.
It's also worth noting that these same drawbacks of target date funds apply to any index fund, compared with doing your own tracking of an index. By buying individual stocks and balancing them yourself, you could theoretically keep higher-dividend stocks in tax-advantaged accounts and low- or no-dividend stocks in your taxable account. You could also do slightly better tax loss harvesting by only selling stocks that have taken a loss, and not an equal portion of the entire index. But these reasons by themselves don't mean it's a good idea to attempt this. Weigh the trade-offs of each approach to decide what works best for you.