@SotiCoto I'd say it's more of a problem of the very structure of the story, rather than being an underdog the readers could sympathise with. After all, if you had an MC that was super successful and enviable in their original world, it would inevitably lead to a situation where the MC would want nothing more than to return to their original world. While wanting to return is not a super rare condition in isekai, generally speaking it's not the only motivation, by far, in the head of the MC (or MCs). Unless the isekai is all about finding the way back, it would just get annoying before long.
That being said, for a RL underdog, like a bullied school kid, just a regular fellow is already something to be envious of. I consider the romantic inexperience of the MCs more of a joke than something that would make them underdogs and losers in life. If you are decently good looking, have a solid job, or are a student doing just fine, there's nothing in particular preventing you from having a romantic relationship. It's just the usual
riajuu, explode joke and the shounen genre virgin status that keeps them inexperienced. It would also be sad to leave a girlfriend or a boyfriend behind when summoned/reincarnated. Actually, that could lead to an infuriating plot. I was going to mention a series name as an example, but it could be a spoiler if you aren't reading it.
