There are plenty of tools out there to create mocks, designs, and brainstorm to no end.
The following describes what I'm looking for in a tool for mocks:

• Alignments - not only should alignments be very strict, I need buttons/shortcuts to auto-align selected elements in the center/left/right. Gimp has a great alignment tool that does exactly this:
• Import / Export - I want to be able to fully import and export everything, not some things. Ideally in text, at a level where one could edit/adjust things manually and not graphically.
• Templating - I appreciate the vast marketplaces that were created for Miro & Figma, really I do, but could I please have a way to quickly grab a group of existing elements, add a few custom inputs, and reproduce them accordingly?
• Versioning - It would be great if we didn't have to reinvent versioning every time a new web app comes out. I've been using version control for 15 years and it's been quite reliable (with the exception of a few newbie git mishaps from 2009 :)). An added bonus is that one could potentially have multiple branches for different sections of the design and easily merge them together (I know that I'm oversimplifying this by a bit).
• Lightweight - This needs to be quick and responsive. My Dell XPS cannot be crawling just because there are more than 4 dialogs in the mock. I'm looking at you Figma.
• Image Search - A quick way to grab images (with the proper license) and use them for designs and mocks has been fantastic. Even better with the new AI engines coming out (DALL-E 2 and the likes).
• Collaborative - I want to be able to quickly share, give/receive feedback, and iterate on designs.

And the winner is...

Nobody! No single solution/app currently out there could do all of these things unfortunately.
The situation is not that dire though, each tool has shown great strengths when used for the right purpose.

The right tool for the right job

I use a combination of all 3 tools at the moment, and each works well doing what it does best:

Systems Design - Draw.io (aka diagrams.net)

Draw.io is a wonderful tool for Systems Design.
It's the most lightweight of the three, allow the creation of complex systems without ever slowing down, and eventually export/import them to XML.
Because of the built-in proper import/export, Draw.io is the most versatile of the group. I was able to embed Draw.io designs in webpages, posts, and at times even in Confluence docs.
Alignment is probably the strongest on Draw.io, and while it's not at the levels Gimp can bring to the table, it's fairly accommodating.
Templating, with a bit of external scripting on top of the XML files, is somewhat doable too.
Draw.io's image search is ok, though the results tend to be more accurate in Miro.
Real-time Collaboration has been recently introduced, but it's still nowhere near Miro or Figma.

Brainstorming and early mocks - Miro

I have to admit, there's something very alluring about the idea of infinite canvas.
In terms of collaboration Miro is hands down the best tool for the job. Figma is a close second, but the freedom to collaborate over so many distinct types of concepts gives Miro the upper hand.
Alignment is pretty good on Miro, though keeping horizontal distance across multiple elements doesn't always work.
Miro is quite heavy, especially when initially loading. One thing I can say is I have worked with companies that had their entire systems, flows, lifecycles, and design mocks on Miro.

Web designs and realistic mocks - Figma

When it starts becoming clear how the app/website should look like, this is where Figma comes into the picture.
Most designers and web developers find Figma to be the last step before actual implementation.
If I had a better sense of design it's very likely that Figma would've been my go-to tool for any mockup.
Figma in 2022 is what Adobe Photoshop was in 2010. It's the go-to tool for web designers and to a lesser extent front-end developers.

Summary

When trying to collect ideas together in a brainstorming session - go with Miro.
When it's time to describe the system in greater detail (especially infrastructure and backend) - go with Draw.io.
When you need to show what it should actually look like for the users - go with Figma.