Spanish, Portuguese or Italian spelling is simpler, consistent, & phonetic, tenses are simpler than English, they're clear, & there are no cases. They still have grammatical gender, though.
Fewer cases than Latin is like saying fewer potholes than Reade's Lane (a road I try to avoid on my road bike except in fine weather & daylight). It's condemning with faint praise. "Not as bad as" =/ good.
And spelling is not inherent to the language. Several languages are written in more than one script. Claiming German is a more sensible language because of its spelling is therefore mistaken. You are confusing the language with how it is represented.
I'm curious (don't worry, it's partly rhetorical, I don't expect you to have the answer), but are 'regular' languages easier to learn? English is famed for irregularity yet seems remarkably easy to learn (sure, people gripe, but they learn it all the same and do a good job). I can say this as someone dim enough to have accepted a bet to learn Japanese which in many ways is quite regular but takes a lot of rote learning and mental re-adjustment (owing to the confidence kryptonite that is beer, I was temporarily of the belief I had developed some kind of learning superpower – I'm just glad I didn't make the same bet in Hong Kong, Cantonese* would reduce my mind to glue).
*yeah, yeah, Hong Kong Cantonese, even worse than Guangdong Cantonese, though they'll fight over that.
I think it depends (clearly) on how you define difficult and regular, and how much of the language you want to learn - just to communicate or to be able to appreciate its literature. (for the record I'd only claim 2, maybe 3 other languages to that level but around 10 to converse, given a little time to brush up in some cases)
Georgian I found relatively easy to learn, as there is one great aspect to it - what you see is what you say. Once you have learnt the alphabet, you can read. That ignores the manifold nuances of the languages that make it a right bugger. However, in practice, the locals were that surprised that anyone had bothered to try we normally managed to converse. In contrast, Mandarin as a tonal language is completely alien to our western brains. Moreover, where in most languages if you try to say something with a bit of goodwill on both sides you can understand each other, in vocal Mandarin that's often impossible if you don't get the sound right - don't get me started on regional variations. Thankfully, if you have learned to write a little communication is possible (which was a bit of a lifesaver for me).
In short, the difficulties aren't really regularity or irregularity - all languages have their quirks - but how closely it fits to the neural pathways of our brains. Japanese, with an alphabet(ish) is much closer than Mandarin in that respect.
Must get on with learning some Thai for the summer hol.