Let me tell you why they do this. As a guy its a bit hard to 'get', but its quite simple really. If shes being blunt or directly honest, the odds of this turning into some kind of shitstorm are quite high. If she tells you she isnt interested, she is worried that this will turn into you asking her why, which will be very uncomfortable to say the least. She doesn't know how a guy might just flip out and start calling her names out of nowhere (which sadly, just as much as theres apparently a lot of guys sending dick pics out there, is rampant). Guys have a tendency to go potentially violent either verbally or whatever, in good parts because most guys put girls on a pedestal. She cant know how telling you will turn out, but to them theres like literally almost 0 good reason to tell you directly vs not telling you. If she doesnt tell you, she avoids a host of potential issues. Plus, if it ever were true and there were good reasons for said reschedules, it kinds of shows how desperate you are (ie: put girls on a pedestal). This is kind of an indirect test in which you can only make yourself more of a turn-off (but it doesnt matter because she isnt interested anyway).

I know from a guys perspective its easy to assume that because you're communicating it means its going somewhere, but experience will make you realize those clues.

Try to think of it this way. Girls get like something between 5-50 messages per day on dating websites, depending on how active they are (of course this varies a lot). Thats without them sending any messages first. She can easily get another date without even trying. The point isnt that you have to stand out as a person, its just that its very easy for them to gauge when a connection is very good vs when its not as good. I've been on many many dates and when it truly clicks in person its few and far between, something i wouldn't necessarily expect guys to recognize until it happens. I do expect girls recognize this far more readily. To anyone that has lived a truly strong connection, it doesnt make as much sense to see someone being super interested in maintaining (ie: have a 2nd+ date) a relationship; it's a lot easier and makes more sense to try again for someone else where it just might (and from their perspective, opportunities are plenty so...).