Rob_E

This may be the case. I know that when I moved from a flat, 1-2 mile commute to a 7 mile commute with hills, I was dismayed to learn that I really wasn't in good shape at all. Two hills in particular were a challenge to get up, and one wasn't very big. I just pedaled up them as far as I felt like, and then I walked. If I was feeling stubborn, I could make it up those hills, but I would be beat at the top, so I just hopped off the bike most days as soon as I hit a certain level of effort that I knew was going to leave me exhausted if I kept it up. One day I found that not only had I biked to the top of my small hill, I was unable to remember the last time I had walked up it. Then I noticed that I was making it up the tall hill more often then not. I haven't walked up either hill in longer then I can remember. But it happened so slowly that I didn't even notice, so it may be that you just need to stick with it and focus on enjoying the ride. If you focus on progress that seems to slow, it can be discouraging, but if you find a way to enjoy your rides regardless of your fitness, you will keep at it and the leg strength will come.

Other things to look into are bike fit, your saddle, and maybe even your gearing. A bad fit can make the ride a lot more work than it has to be. I've found that a bad saddle can make it feel like my circulation is compromised, which means I'm effectively starving my legs while trying to get more out of them. And lowering the gearing to the lowest possible option (and I mean changing out the physical cog/chainring if it's not already at the lowest possible set-up, not just downshifting) will make certain you have every option to pedal up the hills if that's what you want. When you find that the lowest gears are being neglected, you can switch to a higher geared set-up.

And if you really feel like you may be physically unable to gain leg strength, it might be worth consulting a doctor, physical therapist, and/or trainer. I suspect that if this is an area that you've traditionally neglected, then it's more a matter of time and perseverance then ability, but if you suspect otherwise, you should examine those options because a professional will likely have advice for addressing or working around any physical issues.

But I wouldn't worry about the weight. A lighter bike would be easier, sure, but you will acclimate to the heavier bike and be stronger for it. Here on the utility forum and in touring, you will routinely find people pedaling up hills on bikes that are heavier than yours once they've been loaded up. The important thing is that you like your bike enough to want to ride it. I have an old, heavy, upright, 3 speed bike that I picked cheap on Craigslist that used to get out a lot more then my shiny, new, aluminum hybrid. It was just more fun to ride, and if you can keep the fun parts outweighing the work parts, you can't help but become a stronger rider.