Italian economy wasn't so bad until they joined the euro. The northern part still has decent industry even now.

This is unfortunately a populist trope (here in italy) hijacked by no-euro, no-europe, no-nato that need some data/debunking:

Italy is economically coasting since the 1980s, basically since the termination of QE of Bank Of Italy toward Italy Treasure in 1981, and since then politicians struggled to finance their banana republic policies resulting also in less subsidies that boosted businesses, lowering growth. Tangentially Italian business culture is rooted in nepotism and old ways of doing things (basket case of low trust society), so most of companies stay at a family level and new ideas tend to come from family members/offsprings. Capitals are mostly obtained through lending based on superficial personal connections at banks (harder to get financing since 2008) on "clean" balancesheets that in some sectors cover less than 50% of real revenues (small companies found easier to cheat on taxes). R&D expenditures on GDP averaged around 1% since 2000.

TLDR: Italy always has been addicted to subsidies and stimuluses backed by debt to grow on paper, most companies didnt innovate/grow past family businesses in semi-informal economy in the last 30-40 years and now the overrall economy finds really hard to compete/grow. Plus the Pension system is a TITANIC unfunded liability similar to social security but already in deficit waiting for a gigantic wave of baby boomers to enter pension earlier due to whatever populist scheme politicians foster (Quota 103, Opzione Donna, etc...). A lot of retirees lower also internal consuption, weaking the economy further

Regional variance applies, some areas (usually in the north) are competitive/dynamic "globally" and others are on "life support"

Italy success was largely being a proto-China (or proto-Vietnam) before those existed. Basically no respecting copy right and producing knock of stuff.

But has it really been only the now-absent lira rollercoaster that kept the economy afloat? I'm far from convinced that an independent currency would have been a decisive advantage in dealing with the economic challenges of the recent decades, they might even be in a worse position without the euro (not speculating that they would, just refusing to take the other outcome as a given)

I know, I have been visiting Italy since the 1990s and the change is heart-wrenching. It used to be a much more dynamic and optimistic country. Now it feels ... drained and exhausted.