I literally only have a cloud subscription for fireworks, I may be in a massive minority but I find it by far the quickest and most productive tool for basic web graphics / layout. I'm really not interested in the two dozen different apps they've tried to replace it with over the years that attempt to do more than I want and just get in the way.
My understanding is that once you upgrade to Mac OS High Sierra you will no longer be able to use Fireworks because it is not 64bit. I've used Fireworks like forever, so I'm going to not upgrade until I have to. I believe that Illustrator is the actual tool to replace it with, not Photoshop.
The company behind Gravit Designer started out with creating a Freehand-like design tool for their own internal workflow purposes when Adobe decided to discontinue Freehand (Gravit has an interesting backstory). Since their revenues are generated by their work, and not by Gravit Designer, they decided to release it for free.
It's a pretty cool Fireworks alternative, in my opinion: it supports slicing, multiple device asset export (png, svg, jpg), symbols, pages, styles, an so on, but updated to work in more up-to-date web and mobile design workflows. Even master pages are available!
I agree with everyone else for the purpose Fireworks was created, it's the greatest thing since sliced bread. I use it even with High Sierra. I used the 5.1 version but had to download a very old version of Java to work. I just recently added DreamWeaver to my subscription. I have a website I used DW 5.1 and FW 5.1 to create and maintain. I am not a rich person, and I am getting to my maximum for subscriptions.
Gravit Designer is vector-based, but it should open any standard PNG file (just drag and drop a PNG file on the Gravit Designer canvas). If this doesn't work, Gravit might not be able to understand the FW PNG files. Not sure, I haven't tried this myself.
Dreamweaver is no longer the tool it used to be (at all). Adobe just doesn't know what to do with their tools and modern web development, unfortunately. Perhaps try Pinegrow, a visual editor, instead, which is less expensive as well, and you get a full license (or choose the sub option). Both are less expensive than renting Dreamweaver.
I do most of my work in the html ("code" view but like the way I can see the results in real time in the DW interface. So far, I haven't found an HTML editor that works this way, with the smoothness that DW does.
However, Pinegrow is mainly meant for visual editing. That said, when you install the free Atom code editor (I linked to it before) and install the Pinegrow package (plugin) in Atom, any change in either application is updated in the other while you type (no need to save). It's quite powerful. Atom is a beautiful code editor and extremely configurable.
Put both side by side, and you'll have a more or less identical experience as DW - with the advantage of Pinegrow being a much more advanced visual editor, as well as Atom being a "better" code editor.
That's not too surprising. Fireworks was/is a Creative Suite product that has not been updated in many years. The installers are not compatible with Sierra much less High Sierra. See the workaround described below.
Hopefully it'll keep running like a champ for you. Mine crashes about half a dozen times per week on Win10, on average, no matter what compatibility mode it's in. Adobe's made it pretty clear that they have no intention of fixing this.
I've already resigned myself to having to re-create some old graphics that use Adobe's proprietary additions to PNG to enable layering and such. But I can say with certainty that I won't be doing it with any Adobe software. The day Fireworks stops working altogether or just gets too crashy to put up with, I'll be canceling my subscription.
Everything else that I use in CC I can find replacements for already, most of them FOSS. I use the other software (DreamWeaver, Premiere Pro, etc.) because as long as I'm paying for it, I might