Anything on Project Gutenberg has to be in the public domain. So you will only find things based on print editions that are 80 years or more old (exact oldness varies depending on regional rules as to what constitutes 'public domain').
If these happen to be abridged editions, the blame resides with the person who contributed it to PG. Someone needs to do the unabridged edition and contribute that. (why have abridged editions on PG at all?)
And of course many of these are still 'in print' and can add value with introductions or notes.
It's interesting that there were abridged editions, presumably with blessing of the publisher. But these exist even now, for some contemporary books (indeed, there are platforms that offer these exclusively). Some great books are very long and there are people without time to read them who make do with condensed versions to at least have some sense of what they are about.
Translated works are another issue. Again though the original work might be in public domain, the best translations of them will often not be. And there is a lot of subjective judgement about what constitutes a good translation.
Formatting of public domain ebooks is another issue as well. PG is not necessarily doing beautiful or consistent formatting. So there are places like
Standard EBooks that try to do a better job of it.
Kindle Store is a mess, since there can be dozens of editions to sift through and they're of highly variable quality. I usually get Delphi 'Complete Works' omnibus editions of the authors I'm interested in. And Kindle Unlimited has several hundred public domain books with audiobook companions, which avoids the mess as well.