If you think another form of energy production is better, that's a perfectly reasonable objection. Twisting the discussion into a debate over the precise definition of "investment" is silly.
Investment:
> Property or another possession acquired for future financial return or benefit.
Invest:
> to commit (money) in order to earn a financial return
> to make use of for future benefits or advantages invested her time wisely
> to involve or engage especially emotionally were deeply invested in their children's lives
Clearly you can outlay capital now for a future benefit tomorrow that isn’t just your original capital back + the investment. Making sure you’re energy supply is stable so that your economy is working better and your national security is a bit more stable seems like a clear ROI even if you don’t make your capital back + profit directly (it does have potential indirect financial benefits too though).
If that is the bar you're going to use for "investment", then no power generation spending is ever an investment. Not coal, not batteries, not geothermal, not renewables, nothing...
Because none of the above make their cash back plus a profit; they're all subsidised by taxpayers.