Again, specific to Alsace: because of climate change, harvest windows — even for top domaines — are sometimes shifting back into August, which was previously almost unheard of. So it’s probable that some winery folks are moving up their vacations. And if you’re visiting in late July, that might be an issue. (FWIW, though, even normal August vacations mean shutting things down and/or last-minute prep in July, so it’s not usually a great time to visit smaller houses anyway. Though not as bad as trying to visit small houses during harvest.)
But it’s improbable that decent to good houses with established, no-appointment-necessary tasting rooms aren’t open in July. So you might not be able to visit Albert Boxler, but Hugel’s tasting room is certainly open. (In fact, it’s even open in August; I just checked.) Ditto the two Dopffs, and several other producers who’ve quite consciously placed tasting rooms in the most-visited village in Alsace. You can taste some eau-de-vie as well, if that’s your thing, both from the wineries and from dedicated distillers. There’s an entire day of tasting plus tourism in a village you were probably going to visit anyway, without even having to get behind the wheel.
Extremely tourist-oriented villages like Eguisheim, Kaysersberg, Ribeauvillé, Obernai, and so forth will have no lack of options. You’ll taste more and _much_better if you can make appointments, but at least you can taste.
I do find it somewhat unlikely that appointments aren’t available at certain houses, though. Trimbach, for example, has around ten people who could run you through a quick (meaning about two hours’ worth) tasting, and while not all of them bear the last name Trimbach, with enough notice (and no requests for a weekend tasting, or a lunchtime tasting, which almost no winery in France is going to accept unless you’re very, very important) and — this is key — enough flexibility in dates/times, there almost has to be someone around. Just down the road from Trimbach, Kientzler has a regularly-staffed tasting room. There are several other open tasting rooms in Ribeauvillé, and I doubt any of them would close before August vacation. Etc.