twitter.com/astraiaintel/status/1695774263834292397
I think cautious optimism is more than warranted. There are a multitude of good indicators that Ukraine has achieved what they have been trying to set up these last 2 months.
1.) Depending on the map, Ukraine is already at or has even begun breaching the second line, although where it is closest to the first. The Russian defenses don't really form exactly into 3 distinct and totally separate lines. And it took them about a week or so after breaching the first line in force, so the second line, as expected, is not nearly as strong as the first line. Ukraine has been making meaningful advances in the area for more than a week straight now. Primarily because:
2.) Many of Russian units defending that area are heavily degraded. They have been fighting for months without rotation, and have been forced out of strong defensive positions. A sign of this is that Ukrainians are reporting encountering and fighting logistics units. It is unlikely that Ukraine has penetrated to Russia's operational rear (we would see a lot larger and more rapid gains if that were true), but it does mean that some Russian units are having to use their support units to hold the line at places due to too many of their combat line units being too degraded to fight effectively. Also, that Russian forces are getting stretched because:
3.) Russia's operational reserve appears to be depleted. All the reinforcements we have seen in Ukraine on the Russian side recently have been lateral transfers of units from one front/battle to another. In particular Russia's firefighting units (not literal firefighting, but those sent to the hot spots to try to contain the situation) the VDV.
Russia defenses haven't collapsed in the area and Ukraine hasn't broken through, but the more degraded Russian defenders are and the more Ukraine is able to force them backwards, the more quickly Ukraine is going to be able to degrade them further, or even get the chance to destroy some of them. And that can easily lead to a breakthrough.
If Russia doesn't move significant forces to reinforce that area, Ukraine is probably getting pretty close to an actual breakthrough. Russia still has the option of laterally transferring large numbers from other areas, but at the cost of weakening the Russian forces/defenses at those places. Which could lead to interesting developments in those places.
Although, there is still the question of how much does Ukraine have left in reserve to exploit a breakthrough. All of the 12 new spearhead/breakthrough units Ukraine had formed have already been committed to battle, but Ukraine still has other reserves. The Offensive Guard (8-9 brigades, or about a corps) has not been seen much yet, and the length of the offensive so far has provided enough time for some of the Ukrainian units involved in defending Bakhmut, and other areas, to have rested, refitted, and retrained. So Ukraine may still have quite a bit left to exploit a breakthrough, even if it is probably more motorized and light infantry than mechanized.
I would note that despite Russian claims, the 12 brigades Ukraine formed to lead the offensive are also not destroyed or out of action either. If the 47th Brigade, which had a not that great first week and has been doing much of the heavy work breaching the first defensive line near Robotyne, is still in the fight and hasn't had to rotate off the line yet (although some of their battalions may have had to rotate off the line), their losses aren't anywhere near as severe as Russia try to claim. If their claims of Ukrainian losses were true the 47th should have been annihilated several times over.
That is why I think there is a lot of room for cautious optimism here.