I’ll wrap this in a spoiler in case someone wants to watch it.
She didn’t make that much progress during the series regarding her complexes.
She feels overwhelmed in a work environment but at the same time, as a neet, she feels bad about how society judges neets.
She has extremely low self-esteem and even after getting honest, positive feedback she questions her value (“they’re only saying it to be nice”).
Sakurai - while being a shy person himself irl - gets interested in her, and after realising how insecure she is, still tries to be with her.
The progress she made might seem a lot - and for an insecure introvert like her it certainly is a lot. But think about how often and easily she paddled back after getting encouraging words from her friends online. It took a lot of effort and the smallest things can throw her off.
To shortly include this:
Lifetime neet? What’s just asking for problems. Her savings won’t last forever and even if she and Sakurai move in together and he pays all the bills…wouldn’t he get tired of it?
They’re both very humble people and if they have the even smallest thought that they might have offended someone or caused trouble, they apologize like there’s no tomorrow (see apolizing-duel between Sakurai and Morioka).
That said, how long would Sakurai keep doing all the work to support them both until he gets fed up with it?
Possible good scenario: she becomes a housewife (thus not a neet anymore, argue all you want about how being a housewife is or isn’t an occupation), he earns the money. They could live like that even before marrying and if nothing goes wrong they’d probably end up marrying (if they believe it’s necessary for their relationship).
To conclude: them moving in together as a sign of commitment to their relationship and showing how they handle living together (not much, just a short scene or two) would probably be enough for a “okay, we wrapped it up” ending.
Granted, it’s not a huge addition, but it would - at least for me - tie it up better.