Personally, I don't think so.
If a cat spends their life disobeying the warrior code, hurting innocent cats, and overall leading a traitorous and dishonorable life, they don't deserve to be granted StarClan just because they regret what they did in the afterlife. It's unfair to the cats who spent their whole lives putting the needs of others before their own, upholding the warrior code, and making sacrifices for the well-being and safety of their Clan. If a cat reaches StarClan, it's because they've
earned it. Not because they felt bad about their actions while in the Dark Forest.
I think Gray Wing summarized it pretty well.
Juniperclaw narrowed his eyes. “But what if other Dark Forest cats change like Snowtuft did? Is there really no way to earn a place in StarClan even after death?”
Gray Wing looked thoughtful. “We are all judged on what we did in our lifetime. It’s no use being sorry afterward. It’s more important not to break the warrior code in the first place.”
Rootspring thought this was too harsh. “Surely every warrior has done something wrong.” He looked around the others. “Is there any cat here who can say for sure they’ve never broken the warrior code?”
I'm sure every cat in the Dark Forest regrets the choices they made back when they were alive that led them to the Place of No Stars. But simply because you feel regret and even try to redeem yourself (like Snowtuft did), it doesn't mean you get access to StarClan's hunting grounds because it defeats the whole purpose of being a warrior. A cat earns their place in the afterlife - whether that's StarClan or the Dark Forest - based on their actions and decisions back when they were alive; not how they feel after they're dead. StarClan was never meant to be easy to achieve, anyway.
As for what Rootspring said, plenty of cats broke the warrior code, but still earned StarClan in the afterlife. Bluestar broke the code by being in a half-Clan relationship but she atoned by giving up her kits to RiverClan. Hollyleaf broke the code by murdering Ashfur and threatening to kill her own mother but she atoned by sacrificing her life for ThunderClan in the Great Battle. Blackstar broke the code by supporting tyrants and killing Stonefur but he atoned by making ShadowClan strong again through honor and the warrior code, unlike his previous leaders. I assume cats like Snowtuft, Sparrowfeather, and Silverhawk made grave mistakes in their lives but never atoned for them, which was why they ended up in the Dark Forest.
You're supposed to atone for your mistakes when you're alive, not when you're dead. Otherwise, it defeats the whole purpose.