The Observatory has been closed for a while, but looks to me like zero work has been carried out. With the museum closed, there’s literally nothing for tourists in the centre.
I’d look at somewhere like Forbes place, view of the Abbey and town hall and, potentially, nice buildings there. Some cafes, independent brewery, space to sit outside, etc.
for the High St, give space for independent shops and other venues to grow. The change in Dundee, for me, has been impressive. Some great bars and restaurants around and some people have taken it by the scruff of the neck. Independent brands like Hard Grind, Abandon Ship, etc have all flourished.
Paisley has improved from an event perspective, but so little done from a commerce perspective. Not got much faith in the council to do much about it...