There's lots of things, we could do:
Rejoin the EU - our economy is around 4% smaller due to leaving, with new trade deals not making up the loss - challenge is there was a democratic vote to leave and it is unlikely we would be accepted back on the same terms.
Public sector investment to "crowd in" private sector - Manchester is a good example of this, with public money loaned to private companies and a consistent planning process kick starting a building boom, areas having clusters in particular sectors (life sciences/tech/media) increases productivity, improvements to public transport increasing the talent pool available to businesses - challenge is public sector borrowing is already high and therefore you would have to convince bond holders that the investments will pay for themselves.
Energy is far too expensive in this country and in Europe, with USA multiples cheaper due to indiscriminate fossil fuel usage, making it very difficult for any energy intensive businesses to compete. Investment in renewables, battery storage and interconnectors with Europe to efficiently trade energy will result in much cheaper prices in the long run, but the challenge is it is massively expensive to build the infrastructure and stop utilising old infrastructure.
Training and education, there are massive skills and qualifications gaps, along with very little training in how to effectively manage people. If you are employed, unless you are willing to pay for training yourself it is very difficult to move industry post school education. With AI looming it is vital that people are able to use this technology or move industries. The government should give people the opportunity to retrain, but again this would require more spending with no guarantee on return.
Housing, especially council housing, needs building. As builders have merged, they have become more risk averse, sitting on large land banks and only releasing land where sufficiently high enough sales prices can be achieved. The green belt has also massively constrained where you can build in the key places (commutable distances from large cities) where you would want to build. Again the government would need to make an investment case for borrowing more to build. There could also be rules around not allowing builders / investors to sit on land for too long. Major challenges here as we do not have enough trained builders and there is a limit to how many houses you can build whilst maintaining a sufficient profit for private builders and there are benefits for wildlife of retaining greenbelt.
We can't cut or deregulate to prosperity as some politicians would have you believe (well you can but not without creating massive harm). The economy is made up of people, government and business investment, plus external investment. People and businesses have not had a stable environment to invest and a higher tax burden and overcomplicated tax system has sucked money out of the economy. We can attract foreign investment but that ultimately will see the investors extract money. Therefore, it is my view the best way forwards is for the government to make the positive case for investing in people and infrastructure by borrowing more based on future revenue and also reducing trade friction with Europe. This will aid in creating good jobs, lower energy costs and a property market not based on treating property as an ever appreciating asset rather than a home.