What the common entries actually mean
In plain English, with the honest verdict on each.
Excluded by "noindex" tag
Google found the page and found a noindex instruction, so it left it out. That is the tag doing its job. On a thank you page, a cart, an internal search result or a staging path, this is correct and you should do nothing. It is only a problem if you did not intend the tag, which happens when a build time noindex survives launch. If the excluded page is one you want found, that is your bug.
Duplicate, Google chose a different canonical than user
You pointed at one page as the canonical; Google looked at the signals and chose another. This sounds like a rejection and usually is not. If the page Google chose is a reasonable representative and it is indexed, your visitors get there. Look into it when the choice is genuinely wrong, such as a filtered URL beating your real product page, and then fix it by making your intent consistent rather than by adding more tags.
Crawled, currently not indexed
The ambiguous one. Google read the page and passed on it for now, giving no reason. There is no error to fix, which is exactly why it frustrates people. Read it as a quality and demand signal: the page may be thin, may duplicate another of your pages in substance, or may just be new. On a few low value pages, ignore it. On your main service pages, it is telling you something about the pages themselves.
Discovered, currently not indexed
Google knows the URL exists but has not fetched it yet. Common on large sites and new sites. Often it resolves on its own. Where it persists across many pages it can indicate crawl budget being spent badly, or a site that is not giving Google enough reason to come back.
Blocked by robots.txt
Correct behaviour when you blocked it deliberately. Worth knowing the nuance: this blocks crawling, not indexing. A blocked URL can still appear as a bare listing with no description, because Google knows it exists but was never allowed to read it. If you genuinely want a page out of search, noindex is the tool, and Google must be allowed to crawl the page to see it.
Submitted URL blocked by robots.txt
This one is a real contradiction and deserves attention. You put the URL in your sitemap, telling Google you want it indexed, and then blocked it. Two instructions, opposite directions. Decide which you meant.
Soft 404
The page returned a success status but looks empty or like an error page to Google. Common on genuinely thin pages and on custom "not found" pages that forget to return a 404 status. If the page has real content, it is a hint that it reads as empty.
Server error (5xx)
Always worth attention. Your server failed while Google was there. If it is intermittent, it may be load, a timeout or a host problem. Repeated failures make Google crawl less, which affects everything else.
Page with redirect
The URL redirects, so it is not indexed under that address. This is what redirects are for. Normal after any redesign with a proper URL migration.