I don't know what airline you worked at but my former airline has over 4000 pilots retiring in the next 10 years. If you join now you will be a widebody captain in less than 15 years and a narrowbody captain sooner than that.
I am not sure how this statement can be true. The most junior 777 Captain at my airline is around 17%; basically about number 2,100 out of 12,000 pilots. If half the seniority list retires in 10 years after the day you are hired, you would be about number 6,000. Nowhere near WB Captain. 15 years will not get you much closer. We do operate a mixed 757/767 fleet; but again, only the most senior pilots in that fleet frequently fly the 767. I posted in detail what you would be able to hold in 10 years at the legacy I work for. The choices were junior NB Captain, senior NB FO, mid-range WB FO. That is if everything works out perfectly; no economic downturns, no reduction in size for the airline.
The only reason I am focusing on the WB CA position is because that is where the highest pay and best schedules that are so often quoted on PPRUNE exist. I would mostly base career decisions on total compensation, schedules, financial stability and growth prospects of the airline, and probably time to command because that will affect your total compensation. Emirates hands down beats all US legacy carriers in these four areas. The only reason to come to a US legacy is if you really need or want to be back home. Even that comes with a caveat because chances are slim that you'll be based where you would like to reside. Commuting can completely destroy your schedule and quality of life. Some of our most sought after domiciles are extremely senior. It would take years just to hold a reserve NB FO position.