Negotiating equity at a mature startup
I'm a SWE with 5-7 years of experience at a public company in a niche industry. The company experienced substantial growth (AI tailwinds) and I made out very well, but I'm feeling a bit stuck and I don't think the company has much upside. I have other issues with the company but they're not relevant; regardless it's a good time to switch I think. I am bored of the work and I am not learning.
A mature (valuation low billions) is offering a compensation package below my current comp. My current (appreciated) comp is in the high $300ks and the startup is offering $200k + options. The options package is worth around $90k/y assuming a recent strike and share price I found on a salary comparison website. The company probably will do well and grow some, it could 10x, but a single digit multiple is perhaps more feasible.
The new job is fully remote which is nice (though I barely go into the office as is).
All that said, I do want to switch, but I can't help but feel this offer is not so great. How do I approach this situation? Given the nature of the offer I wouldn't expect a substantial counteroffer from my employer, and I'm not sure a counteroffer would move the startup offer that much given it's already lower than my current comp. Do I just say "I am established and well compensated at my current job and I don't feel this is enough, would you offer $xx" (phrasing TBD) and cross my fingers, or is there a sensible way to play hardball here?