If you mean something like Voyager traveling through the Delta Quadrant in 1995-2001 or in centuries previous...
The Vaadwaur had a giant space empire stretching to Talaxia. The Voth were probably still there, though the Vaadwaur would of had to go around them (the Voth seem to be the wall holding back the Borg). The Borg were very minor when the Vaadwaur were at their peak, so the vast Borg empire might not be a problem then. The Krenim Imperium might've been stronger too.
Let's see the major races on their journey.
- The Caretaker, can't go back before 1500 years ago because that's when they arrived at Ocampa. No Caretaker, no means of pulling Voyager there.
- No Kazon. They's all be slaves. Not sure how the Trabe would be at their peak or even if their warp goes back centuries. Kazon just took control decades earlier.
- Vidiians. Gotta go back 2000 years to avoid the Phage versions of them.
- No Tackleberry and the '37s if its back before 1937. If it's around then, there should be a quicker way back if Voyager gets their technology. We know nothing about how Briori got and used humans as slaves (sounds like the plot of Stargate) or where they event went since 1937. Why slaves so far away when they could just raid the Trabe for the Kazon isn't clear.
- The Cravic & Pralor androids seemed to be focused on fighting their builders' war rather than outsiders.
- The Swarm, we don't know how long they were there, if their space grew over the decades/centuries or if it just shifted shape.
- The Voth would still be around there.
- The Borg back around 1500 only controlled a handful of star systems. Looking at species numbers and distances, it seems like their control expanded exponentially in the past century or so. Who knows when or where they got transwarp. Do Borg develop new technology (besides that associated with the collective itself) or just steal it from other races? If so, that means the green transwarp race is out there and was assimilated. Borg conquest likely accelerated when they got transwarp.
- The Krenim had big space (across 5000 parsecs, over 200 star systems) and the fact Annorax's ship never went after the Borg indicates the Borg were never an "enemy" to the Krenim or else they would have erased their existence (maybe the Borg detected the fluctuating timelines and chose to stay far away, unlike nearby areas like the B'omar. I think the Voth are one wall on Borg territory and the Krenim time flux is another wall, which is why early/late Season 4 space are so different vis a vis the Borg). Annorax is from early in their decline (2170s), so anytime before is the Krenim at their peak, and at various points after, they were at their peak.
- The Hirogen... according to the map, their communication array exists across the whole middle swath (from the core) of the Delta Q and is actually more widespread in the deep of the Beta Q. They seem to have been around and advanced longer than any species but the Voth, though haven't changed in at least 1000 years. They've been advanced enough to avoid Borg detection as a unique culture. Seven didn't know of them despite a few Hirogen being in Unimatrix 0, meaning they've only captured stray hunters here or there.
- Species 116 wouldn't have been assimilated. Their low species number (close to the Borg Queens) indicates they are most likely one of the earlier encountered species, indicating closeness (or their slipstream ships traveled to early Borg space). They managed to resist for centuries but for whatever reason, right before the 8472 war, the Borg had almost won. The fact Borg don't use slipstream indicates transwarp is probably easier (but they should understand it with the assimilation of Arturis' species). They might've been friendly and helpful back before the Borg siege.
- Moneans would have been on the waterworld for 300 years and it existed for 100,000 years. Its original builders were likely long gone.
Season 5 space is choppy due to all the different jumps. Some of those jumps wouldn't have been possible in the past.
- The Vaadwaur, their underspace network spanned Talaxia to some distance past the Vaadwaur homeworld. Problem is they were ***holes, so getting use of that network wouldn't be possible for 1 starship.